The primary purpose of the passage is to
A．(A) point out that theories about the functioning of olfactory sensation have failed to change despite experimental inquiry
B．(B) suggest means by which the impact of odors that irritate human subjects may eventually be lessened
C．(C) describe the attempt of scientists to understand the degree to which odor perception is learned or innate
D．(D) demonstrate that efforts to understand the psychobiological basis for human perception is too difficult for modern laboratory techniques
E．(E) describe how the emotional pairing process in odor sensation can lead to the experience of irritation
