Researchers studying how genes control animal behavior have had to deal with many uncertainties. In the first place, most behaviors are governed by more than one gene, and until recently geneticists had no method for identifying the multiple genes involved. In addition, even when a single gene is found to control a behavior, researchers in different fields do not necessarily agree that it is a “behavioral gene.” Neuroscientists, whose interest in genetic research is to understand the nervous system (which generates behavior), define the term broadly. But ethologists — specialists in animal behavior — are interested in evolution, so they define the term narrowly. They insist that mutations in a behavioral gene must alter a specific normal behavior and not merely make the organism ill, so that the genetically induced behavioral change will provide variation that natural selection can act upon, possibly leading to the evolution of a new species. For example, in the fruit fly, researchers have identified the gene Shaker, mutations in which cause flies to shake violently under anesthesia. Since shaking is not healthy, ethologists do not consider Shaker a behavioral gene. In contrast, ethologists do consider the gene period (per), which controls the fruit fly’s circadian (24 hour) rhythm, a behavioral gene because files with mutated per genes are healthy, they simply have different rhythms.

The primary purpose of the passage is to
(A)summarize findings in an area of research
(B)discuss different perspectives on a scientific question
(C)outline the major questions in a scientific discipline
(D)illustrate the usefulness of investigating a research topic
(E)reconcile differences between two definitions of a term

OA:B but isn't that is narrow in scope. Whether it is 'behavioral gene' is the scientific question but there are other elements as well. B ignores first 2 lines. Primary purpose is to "present the challenges faced by researchers". Among options, i find C most close but "questions" is a bit iffy.