instruction:
Given a scientific passage and an answer, generate a question for the given answer.
question:
Passage: Conditioning is a way of learning that involves a reward or punishment. If you ever trained a dog to obey a command, you probably gave the dog a tasty treat each time he performed the desired behavior. It may not have been very long before the dog would reliably follow the command in order to get the treat. This is an example of conditioning that involves a reward. Answer: conditioning
answer:
The way of learning that involves reward and punishment is called?

question:
Passage: After the film is developed, any unexposed silver bromide must be removed by a process called "fixing"; otherwise, the entire film would turn black with additional exposure to light. Although silver bromide is insoluble in water, it is soluble in a dilute solution of sodium thiosulfate (Na2S2O3; photographer's hypo) because of the formation of [Ag(S2O3)2]3 ions. Thus washing the film with thiosulfate solution dissolves unexposed silver bromide and leaves a. Answer: fixing
answer:
After the film is developed, any unexposed silver bromide must be removed by a process called what?

question:
Passage: Populations gain individuals through births and immigration. They lose individuals through deaths and emigration. These factors together determine how fast a population grows. Answer: individuals
answer:
What do populations gain through births and immigration?