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

[Q]: Passage: For feeding, the insect head contains one pair of lower jaws and two pairs of upper jaws. Insects have also evolved a wide range of specialized mouthparts for eating certain foods. You can see some examples in Figure below . Answer: two pairs
[A]: How many pairs of upper jaws do insects have?

[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
[A]: The values of which factors are controlled by the experimenter over the course of an experiment?

[Q]: Passage: Rising and sinking air can influence the precipitation of a region. Answer: precipitation
[A]:
What does rising and sinking air influence in a region?