PrepTest 117, Section 1, Question 16

Working the answers

• A
  Correct

  This initially takes more work than matching a quotation. The final paragraph explains where developing nerves receive NGF and how it guides their growth and supports survival. Discovering the substance therefore helped researchers understand processes governing development of the nervous system. That is the broader advance the details illustrate.

• B

  Tissue culture was a new technique used in the investigation. The writer doesn't present demonstrating that technique's usefulness as the primary significance of discovering NGF.

• C

  The programmed-death hypothesis began the research, and the finding of excess embryonic cells belongs to that earlier stage. This doesn't capture the broader significance of identifying the substance that regulates development and survival.

• D

  Different species do appear: mouse tumors, chick embryos, and animals including humans. But the writer doesn't make cross-species activity the principal reason the discovery matters. A better captures what the later research explains.

• E

  This accurately describes the substance identified in the experiment. It stops at what was found, though, rather than explaining why finding it advanced our understanding. A connects the discovery with the larger processes it helped explain.