One of the requirements for a fire is that the material ___to its burning temperature .
问题描述：
One of the requirements for a fire is that the material ___to its burning temperature .
A.were heated B.must be heated C.is heated D.be heated
选择哪个?理由?
答
D
require that +（should） do：要求……,其中should可以省略.
再加上被动语态,所以应该是be heated.
这句话的意思是：燃烧的一个要求是物质应该达到其着火点.