Answer the following question: You are presented with the quiz "Where photosynthesis occurs in a cactus, what is stored?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "acactus stem is used for storing water" and "photosynthesis occurs on the green surface of the cactus stem". So, what's the best answer to the question?

Choices:
*glucose
*flowers
*water
*sand
*gametes
*birds
*lipids
*energy
Answer:
water