Question: Researchers recently discovered a gene in humans that previously was unknown to science. Which statement best explains why the gene probably was not discovered much sooner?

  Options: 
 A. The gene only recently evolved in humans.
 B. The technology used to study genes is still being developed.
 C. Scientists were not interested in genes until a few years ago.
 D. Scientists were sure they had already discovered every possible gene. 
Answer: B