What does the passage mainly discuss？
A. The research methods used by scientists.
B. Observation and human perception variation.
C. The relation between hypothesis and observation.
D. The human perceptual mechanism.
【B5】
A. combat
B. rival
C. fight
D. defeat
It can be inferred from the last paragraph that human perceptual mechanism ______.
A. can never be changed
B. provides objective and straightforward way for observation
C. can provide some sort of correction on the basis of experience
D. always alters reality
【B4】
A. available
B. excessive
C. incredible
D. applicable
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