单项选择题

The authors statement that "psychology holds a unique position among the sciences" (lines 4--5) is supported by which of the following claims in the passage

A.The full meaning of a human relationship may not be obvious.
B.Commonsense understanding of human relations can be incisive.
C.Intuitive knowledge in the physical sciences is relatively advanced.
D.Subjective bias is difficult to control in psychological researc