单选题
It is required that such insulator (绝热体) ______ a heat resistant material.
A、
must be made of
B、
should be made of
C、
will be made of
D、
would be made of
【正确答案】
B
【答案解析】
在“It is required that…”句型中that从句中要用虚拟语气，其表示方法是should do。类似的还有“It is desired that…”，“It is suggested that…”，“It is ordered that…”等。
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