RC 2.130. 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

此题我选择了C，我觉得文章主要是提出了一个学科内的几个有争议或者无法解决的问题。而不是针对一个问题讨论。

原文：

RC 2.128 – 2.130

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

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