Given a scientific question, generate a correct answer to it.

Input: Consider Input: Crossover occurs between non-sister chromatids of which chromosomes?

Output: homologous

Input: Consider Input: When scientists work in natural settings rather than a lab, it is called what?

Output: fieldwork

Input: Consider Input: One of the simplest machines is the lever, which is a rigid bar pivoted at a fixed place called what?
Output: fulcrum