Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: The bottom two chambers of the heart are called the left and right ventricles. The ventricles receive blood from the atria and pump it out of the heart, either to the lungs or to the rest of the body. Answer: ventricles
[EX A]: What structures receive blood from the atria and pump it out of the heart?

[EX Q]: Passage: Some nonmetals are very reactive, whereas others are not reactive at all. It depends on the number of electrons in their outer energy level. Answer: reactivity
[EX A]: The number of electrons in the outer energy level determines what property of nonmetals?

[EX Q]: Passage: The first and longest phase of mitosis is prophase . During prophase, chromatin condenses into chromosomes, and the nuclear envelope, or membrane, breaks down. In animal cells, the centrioles near the nucleus begin to separate and move to opposite poles (sides) of the cell. As the centrioles move, a spindle starts to form between them. The spindle, shown in Figure below , consists of fibers made of microtubules. Answer: prophase
[EX A]:
What is the first phase of mitosis?