旧PREP上一道题，还有点小疑惑

何小媛159753

To prevent harbor porpoises from getting tangled in its nets and suffocating, a fishing company installedacoustic alarms on all its boats that fish in waters off Massachusetts.The sound emitted temporarilydisorients the porpoises and frightens them away.Since the installation of the alarms, the average number of porpoises caught in the company's nets has dropped from eight to one per month.The alarms, therefore, are saving the lives of harbor porpoises in those waters.

Which of the following is an assumption on which the argument depends?

(A) The use of acoustic alarms increases the number of commercial fish caught by the fishing company's boats.

(B) When disoriented, harbor porpoises are not significantly more likely to be killed by other boats.

(C) Environmentalists advocate the use of acoustic alarms as a means of protecting the harbor porpoise population.

(D) The alarms were installed at the time of year when harbor porpoises are most plentiful in the Massachusetts waters.

(E) The cost of installing acoustic alarms on fishing boats is less than the cost of repairing nets damaged by harbor porpoises.

这道题选B，我明白，但突然有点小疑惑：文中说the average number of porpoises caught in the company's nets has dropped from eight to one per month.不是就证明了porpoises不会被其他船杀死吗，要不然死亡数量怎么会下降呢，请大家指点迷津

chasingM7

the average number of porpoises caught in the company's nets has dropped from eight to one per month.

=> it says THE COMPANY'S NETS specificly. not other companies.