What does the passage mainly discuss? The purpose of the second mention of "hormones" in line 4 is to point out

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问题 What does the passage mainly discuss?
The purpose of the second mention of "hormones" in line 4 is to point out

选项 A、chemical signals that are common among insects
B、specific responses of various species to chemical signals
C、similarities between two chemical substances
D、how insects produce different chemical substances