Dont use water to put out the fire if oil catches fire. As is known oil float on water

问题补充：

Don use water to put out the fire if oil catches fire. As is known, oil float on water.

A. shall

B. must

C. may

D. will

答案：

A. shall

B. must

C. may

(答案→)D. will

解析：D句意：如果油着火了不要用水来灭火，我们都知道油会浮在水的上面。will用于陈述真理性的事实。