问题
选择题
Gunpowder is generally believed __________ in ancient China.
A．to have invented
B．being invented
C．to have been invented
D．having invented
答案
答案：C
考查固定搭配。Be believed to do…，被认为……，所以排除B,D；且主语Gunpowder和动词invent是动宾关系，所以要用不定式的被动形式，且invent发生在主句谓语动词believe之前，所以用不定式的被动完成时。选C。