(Pasted as received, with an observation in brackets [...])

I would have given him 100%! Each answer is absolutely grammatically [and semantically] correct, and funny too. The teacher had no sense of humor!

Q1. In which battle did Napoleon die?
*His last battle

Q2. Where was the Declaration of Independence signed?
*At the bottom of the page

Q3. River Ravi flows in which state?
*Liquid

Q4. What is the main reason for divorce?
*Marriage

Q5. What is the main reason for failure?
*Exams

Q6. What can you never eat for breakfast?
*Lunch & dinner

Q7. What looks like half an apple?
*The other half

Q8. If you throw a red stone into the blue sea, what will it become?
*Wet

Q9. How can a man go eight days without sleeping?
*No problem, he sleeps at night.

Q10. How can you lift an elephant with one hand?
*You will never find an elephant that has one hand.

Q11. If you had three apples and four oranges in one hand and four apples and three oranges in other hand, what would you have?
*Very large hands

Q12. If it took eight men ten hours to build a wall, how long would it take four men to build it?
*No time at all, the wall is already built.

Q13. How can you drop a raw egg onto a concrete floor without cracking it?
*Any way you want, concrete floors are very hard to crack.