TASK DEFINITION: Given a scientific passage and an answer, generate a question for the given answer.
PROBLEM: Passage: The amount of material left over after a certain number of half-lives can be easily calculated. Answer: pheromone

SOLUTION: What term is used to describe a chemical released by an animal that affects the behavior or physiology of animals of the same species?

PROBLEM: Passage: Many common electric devices, such as doorbells, contain electromagnets. If they have moving parts, they are likely to have an electric motor. An electric motor is a device that uses an electromagnet to change electrical energy to kinetic energy. Answer: electromagnets

SOLUTION: What do electric motors use to change electrical energy into kinetic?

PROBLEM: Passage: The control rods play an important role in the modulation of the nuclear chain reaction (usually a collision of a neutron with uranium). Each collision produces more neutrons than were present initially. If left unsupervised, the reaction would soon get out of control. Rods are commonly made of boron or a number of metals and metal alloys. The purpose of the control rods is to absorb neutrons to regulate the rate of the chain reaction so that the water does not overheat and destroy the reactor. Answer: control rods

SOLUTION:
What play an important role in the modulation of the nuclear chain reaction?