问题补充:
One of the requirements for a fire is that the material to its burning temperature.
A. is heated
B. be heated
C. would be heated
D. shall be heated
答案:
A. is heated
(答案→)B. be heated
C. would be heated
D. shall be heated
解析:句意:对火的要求之一是材料要被加热到燃点。主语是requirement,suggestion,order,advice等词后面的表语从句中用虚拟语气:should do,should可以省略,而且material和heat是被动关系,用被动语态,选B。