One of the requirements for the fire is that the material to its burning temperature. A.

问题补充：

One of the requirements for the fire is that the material to its burning temperature.

A. is heated

B. will be heated

C. would be heater

D. be heated

答案：

A. is heated

B. will be heated

C. would be heater

(答案→)D. be heated

解析：因为requirement后的表语从句的谓语要用“(should +)动词原形”；material(材料)与heat(加热)是被动关系，用被动语态，所以是be heated。