function check(){//interprets and check before launch the quiz 
	var totalchecked=0,index=0; 
	for (i=0;i<6;i++) if (eval("document.form1.c"+(i+1)+".checked")==true) {totalchecked++; index+=(1<<i);} 
	if (totalchecked<2) {
		alert ("You must choose at least 2 fields to continue your training.");
		return;
	}
	initQn(index);
}

function initQn(selected){//launch the quiz with a number of topics selected
	var totalq=10,topics=6;
	var i,j,rand,temp1,temp2;
	var qno=new Array(totalq);
	var index=new Array(0,5,10,15,20,25,30);
	for (i=0;i<totalq;i++){//initialise question number
		j=topics;
		while (j==topics){
			rand=Math.round(Math.random()*(index[topics])-0.5);
			for (j=0;j<topics;j++){
				if ((rand>=index[j] && rand<index[j+1]) && (selected&(1<<j))) { 
					for (k=0;k<i;k++) {
						if (rand==qno[k]) {j=topics-1;break;}
					}
					if (k==i) { qno[i]=rand;break;}
				}
			}
		}
	}
allqn=new Array(
new Array("In which Apollo series mission did the first man land on the moon?",4,new Array("Apollo 10","Apollo 11","Apollo 12","Apollo 13"),2),
new Array("How many missions are there in the Apollo series?",4,new Array("14","15","16","17"),4),
new Array("Starting from which mission did the astronomers start to use lunar rovers?",4,new Array("14","15","16","17"),3),
new Array("When is the last Apollo mission?",4,new Array("1970","1971","1972","1973"),3),
new Array("How many civilian geologists were present for the Apollo 16 and Apollo 17 missions?",4,new Array("2","3","4","non of the above"),4),
new Array("Among the options below, which is not an advantage of building a cluster rocket?",4,new Array("Cheaper than building a large engine to obtain high speed","the failure of a single engine does not prevent continued flight","two stages can be dropped at the same time if a sudden reduce in mass is required","the rocket can share the same tank and other structures to reduce the total mass"),3),
new Array("Since delicate calculations of the launching conditions are needed, the countdown to launch starts ",4,new Array("12 hours before the actual lift-off","24 hours before the actual lift-off","48 hours before the actual lift-off","72 hours before the actual lift-off"),4),
new Array("Which of the following is not a method of rocket guidance?",4,new Array("radio guidance","satellite guidance","programmed guidance","inertial guidance"),2),
new Array("How does the jet fins help with the control of the rocket?",4,new Array("fins are moved to change gas-jet direction","ins are moved to change the air movement","fins are moved to change the air pressure","fins are moved to accelerate the rocket"),1),
new Array("What is the first liquid-propellant rocket launched?",4,new Array("Discovery","V-2","Viking","Saturn-5"),2),
new Array("Which of the following satellites is not launched in 1958?",4,new Array("Vanguard II","Sputnik 2","Explorer 1","Explorer 3"),2),
new Array("NASA was founded partly as a result of the",4,new Array("Cold War","Economic depression","Space race","The launching of Soviet satellite Vostok"),3),
new Array("What did the recently launched Chandra X-ray Observatory studied?",4,new Array("active galactic nuclei ","nebulae","X-ray resources in the outer reaches of the universe","All of the above"),4),
new Array("How many satellites does the US Global Positioning System (GPS) employs?",4,new Array("16","20","24","28"),3),
new Array("Which of the following gives information about the temperature and cloud patterns?",4,new Array("GPS","SMS","HST","ISO"),2),
new Array("Gagarin is the man who:",4,new Array("Died in Soyuz mission","first landed onto the moon","involved in the Gemini mission","none of the above"),4),
new Array("Who said the famous line, 'This is one small step for man, but a giant leap for mankind.'?",4,new Array("Armstrong","Aldrin","Gagarin","Captain Shepad"),1),
new Array("Who performed the first walk in space, the extravehicular activity (EVA)?",4,new Array("Shepad","Glenn","Edward White II","Gagarin"),3),
new Array("Valentina Tereshkova is",4,new Array("the first Russian who walked on the moon","the first woman in space","involved in the Voskhod programme","none of the above "),2),
new Array("Which of the following is a year of tragedy for the Soviet Union and the US?",4,new Array("1965","1966","1967","1968"),3),
new Array("Which of the following part is not reusable in a space shuttle?",4,new Array("External fuel tank","Solid rocket boosters","Payload (cargo)","All of the above"),1),
new Array("Which of the following is not a component of the body of a space shuttle?",4,new Array("External fuel tanks","Solid rocket boosters","Payload (cargo)","Orbiter"),3),
new Array("Which is the largest part of a space shuttle?",4,new Array("External fuel tanks","Solid rocket boosters","Payload (cargo)","Orbiter"),1),
new Array("How many sections (decks) are there in a cockpit?",4,new Array("1","2","3","4"),2),
new Array("How much payload can a space shuttle carry on a return journey?",4,new Array("45 tons","30 tons","20 tons","15 tons"),4),
new Array("Which of the following is not a characteristic of the environment of a space station?",4,new Array("Weightlessness","High-vacuum","Low radiation","Highly solar-powered"),3),
new Array("How many stations are there in the Salyut series?",4,new Array("3","5","7","9"),3),
new Array("Which is the first US space station?",4,new Array("Mir","Salyut 1","Spacelab","Skylab"),4),
new Array("Which of the following has not been abandoned?",4,new Array("Salyut 7","Skylab","Mir","Spacelab"),4),
new Array("Which of the following has not participated in the construction of the International Space Station?",4,new Array("Russia","Japan","China","Canada"),3)
);

	var qntext=new Array(totalq);
	for (i=0;i<totalq;i++) qntext[i]=allqn[qno[i]];
	quizWindow=window.open ("quiz.html");//open the new window and write codes to it
	var doc=quizWindow.document;
	doc.write ("<html>\n\n<script language=javascript>\n");
	doc.write ("function markquiz(){\nvar mark=0,i,j,tspan;\nfor (i=0;i<"+totalq+";i++){\n");
	doc.write (" j=0;\n while (eval('document.form1.q'+i+'choice['+j+']')) { \n  tspan=eval('q'+i+'c'+j); \n");
	doc.write ("if ((eval('document.form1.q'+i+'answer.value')-1)!=j) tspan.className='ignore'; \n");
	doc.write (" else if (eval('document.form1.q'+i+'choice['+(eval('document.form1.q'+i+'answer.value')-1)+'].checked')) {tspan.className='right'; \n mark++; }\nelse tspan.className='wrong'; \nj++; tspan=eval('document.q'+i+'c'+j); \n }}\n");
	doc.write ("alert ('Your mark is: '+ mark+'/'+"+totalq+"+((mark>"+totalq/2+")?' \\"+"nCongratulations!':'\\"+"nNext time please work harder!'));document.cookie='score='+mark+'/"+totalq+"';}\n");
	doc.write ("<"+"/script>\n<style type='text/css'>\n.header{color:darkblue;font: bold 12pt/12pt Verdana, Arial, serif;font-weight: 900}\n");
	doc.write (".question{color: black; font: 10pt/12pt Verdana, Arial, serif}\n");
	doc.write (".answer{color: black; font: 10pt/10pt Verdana, Arial, serif}\n");
	doc.write (".wrong{color: red; font: bold 10pt/10pt Verdana, Arial, serif}\n");
	doc.write (".right{color: darkblue; font: bold 10pt/10pt Verdana, Arial, serif}\n");
	doc.write (".ignore{color: 909090; font: 10pt/10pt Verdana, Arial, serif}\n</style>\n<body bgColor=#ffffff leftMargin=0 topMargin=0>\n");
	doc.write ("<form name='form1' method=post>\n<table width='100%' cellPadding=0 cellSpacing=0>\n<tr>\n<tr>\n<td width=20%></td>\n<td width=20%></td>\n<td width=20%></td>\n<td width=20%></td>\n<td width=20%></td>\n</tr><tr></td><td colspan=5 align='center'><span class='header'>Space Odyssey Training Quiz #1</span></td>\n</tr>\n");
	for (i=0;i<totalq;i++) {
		doc.write ("<tr>\n<td bgcolor=c0c0c0 colspan=5 align='left'><span class='question'><b>Q"+(i+1)+". </b>"+qntext[i][0]+"</span></td>\n</tr>\n<tr>\n");
		for (j=0;j<qntext[i][1];j++) doc.write ("<td align='left'><span id='q"+i+"c"+j+"' class='answer'>"+"<input type=radio name='q"+i+"choice' value='"+(j+1)+"'>"+qntext[i][2][j]+"</span></td>\n");
		doc.write ("</tr>\n<input type='hidden' value='"+qntext[i][3]+"' name='q"+i+"answer'>\n");
	}
	doc.write ("<tr>\n<td align='right' colspan=5><input type='button' value='summit your answer' onclick='markquiz()'></td>\n</tr>\n</table>\n</form>\n</body>\n</html>");
}