单选题
Questions 172-173 refer to the following announcement.
Operation of Detroit's trash incinerator, the largest in the nation, was halted last month, less than a year after it was put into service. The huge plant, which was designed to change waste into energy, had been hailed as an innovative means of putting trash to good use. However, soon after the plan began operating, unhealthy levels of mercury began to be detected in the air around the city. It was soon discovered that the culprit was the new incinerator. Entire neighborhoods were threatened by the toxins being discharged into the air. Environmental officials ordered the plant to be shut down last week. They say it is uncertain when, or even whether, the plant will reopen.
单选题 According to the passage, why was the plant shut down?
【正确答案】 B
【答案解析】The plant was shut down because it was causing unhealthy levels of mercury. Choice (A) confuses too much trash and trash incinerator, the largest in the nation. Choice (C) is incorrect because changing waste into energy was the plant's purpose. Choice (D) is contradicted by the environmental officials shutting it down.
单选题 What was the function of the plant?
【正确答案】 D
【答案解析】The plant's function was to turn waste into energy. Choice (A) is something the plant does but it is not the plant's primary function. Choice (B) is the function of environmental officials. Choice (C) is an unexpected result of the conversion process.