Bears love human food and will stop at nothing if they get a scent of any food; chocolate is also loved by many bears.
After offering Bob a Snickers, he leaves munching on his new treasure, mutering something about "You gonna be bear food" and other such nonsense. You finish your lunch, and start back hiking. You reach a clearing, and see a large bear sleeping on the remains of a expensive looking backpack. You creep around silently, but step on a twig that breaks with a sound like a gunshot. The bear wakes up, and stares at you with bloodshot eyes.
A) Throw a rock at it and hope to make a break for it;
B) Bang some pots and pans together to make enough noise to scare it away;
C) Drop your pack and climb a nearby tree.