TOEFL Reading: ETS-TOEFL阅读机经 - 364519G05TR4863JL$

According to paragraph 7, what happens when a knifefish comes into contact with another knifefish that has a similar discharge rate A. Both fish speed up their discharge rate, perhaps out of a sense of competition. B. Both fish slow down their discharge rate so that they are better able to hear each other. C. One fish increases its discharge rate while the other decreases it, making the signals less similar. D. Each fish slowly changes its discharge rate until they match up perfectly.