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

Passage: Eggs are female gametes that form in the ovaries and are released into the fallopian tubes. Answer: eggs
What are the female gametes that form in the ovaries?

Passage: There are three types of mechanical waves. They differ in how they travel through a medium. The three types are transverse, longitudinal, and surface waves. All three types are described in detail below. Answer: three
How many types of mechanical waves are there?

Passage: Experimental controls are other factors that might affect the dependent variable. They are kept constant so they will not affect the results of the experiment. Answer: experimental controls
In an experiment, what is kept constant so they will not affect the results, including affecting the dependent variable?