题目内容：

    In the trailer (拖车式房屋)，Sischo was refreshing the snails ‘(锅牛）accommodations--an  ongoing routine that takes days of careful work. He had found a dozen of Achatinella bulimoides--a third of the world's population of the species. Once every individual was accounted for, he cleaned the cage and packed in new leaves. The work took much trouble, but the responsibility, he said, was like “a heavy weight sitting on you.”

The trailer is very vulnerable. It’s designed to keep away would-be thieved, and to resist hurricanes. But a fire could easily destroy it, or a disease could sweep through it. Last September , a mystery pathogon（病原体）appeared to have entered the trailer on leaves fed to the snails, killing almost an entire species. As sad as the event was, there’s no good way to insure against future catastrophe. The snails can’t simply be spread among zoos or other facilities: they need special equipment, experienced handlers, and a diet of native Hawaiian plants.

Consequently, it can be hard for the snails' minders to relax, even when they are outside the trailer. “How do you switch off when your decisions mean existence or extinction?" Sischo said. While action lightens the burden, yet with animals whose natural history is largely unknown, that action can be dangerous. "If you do it wrong, the snails die.”

Snails are neither intelligent nor beloved. Sischo's friends sometimes tease him about being "the strange snail guy' ; strangers ask why he cares. It's hard to convince people, but he insists that if he can just get them in the trailer, they will understand why the Achatinella bulimoides are worth saving. "People melt," he said“When you show them that the entire population is in this chamber, it hits them."

1.What is the trailer used for?

A.Accommodating guests B.Sheltering snails

C.Planting vegetables. D.Alarming thieves.

2.What does the underlined word “vulnerable" mean in paragraph?

A.Quite. B.Safe.

C.Easily affected. D.Well protected.

3.What is the snail minders' attitude towards their job?

A.Relaxed. B.Confident.

C.Cautious D.Disapproving

4.Which of the following could be the best title for the text?

A.The Last of Its Kind B.The Worst of Times

C.Mourn Its Loss D.Resist Possible Dangerous