(C) begin

　　(D) rely

　　42. The purpose of the second mention of "hormones" in line 4 is to point out

　　(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

　　43. The word "sole" in line 6 is closest in meaning to

　　(A) obvious

　　(B) best

　　(C) only

　　(D) final

　　44. The passage suggests that the speed at which communication through pheromones occurs is dependent on how quickly they

　　(A) lose their effectiveness

　　(B) evaporate in the air

　　(C) travel through the air

　　(D) are produced by the body

　　45. According to the passage, the meaning of a message communicated through a

　　pheromone may vary when the

　　(A) chemical structure of the pheromone is changed

　　(B) pheromone is excreted while other pheromones are also being excreted

　　(C) exocrine glands do not produce the pheromone

　　(D) pheromone is released near certain specific organisms

　　46. The word "detecting" in line 23 is closest in meaning to

　　(A) controlling

　　(B) storing

　　(C) questioning

　　(D) finding

　　47. According to paragraph 2, which of the following has made the study of

　　pheromones difficult?

　　(A) Pheromones cannot be easily reproduced in chemical laboratories.

　　(B) Existing technology cannot fully explore the properties of pheromones.

　　(C) Pheromones are highly volatile.

　　(D) Pheromone signals are constantly changing.

　　48. The word "They" in line 24 refers to

　　(A) pheromones

　　(B) roles

　　(C) activities

　　(D) insects

　　49. The word "sedentary" in line 29 is closest in meaning to

　　(A) inactive

　　(B) inefficient

　　(C) unchangeable

　　(D) unbalanced

　　50. Pheromone systems are relatively complex in insects that

　　(A) also communicate using sight and sound

　　(B) live underground

　　(C) prey on other insects

　　(D) live in organized group

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