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

[EX Q]: Passage: Hinge Joint. The knee joint is a hinge joint. Like a door hinge, a hinge joint allows backward and forward movement. Answer: hinge joint
[EX A]: What type of joint is the knee joint?

[EX Q]: Passage: A variable is a factor that can change over the course of an experiment. Independent variables are factors whose values are controlled by the experimenter to determine its relationship to an observed phenomenon (the dependent variable). Dependent variables change in response to the independent variable. Answer: independent variables
[EX A]: The values of which factors are controlled by the experimenter over the course of an experiment?

[EX Q]: Passage: The radiation exposure is determined by the number of rads times the quality factor of the radiation. Answer: rads
[EX A]:
The radiation exposure is determined by the number of what times the quality factor of the radiation?