Who do you think was generally considered （ ）the lamps?A inventing B to invent C to have inventWho do you think was generally considered （ ）the lamps?A inventing B to inventC to have invented Dhaving invented 为什么选C啊

这句话的意思是：你认为是谁发明了电灯？
consider sb to do sth是认为某人做了某事。而发明电灯这件事已经是做完的事情了，所以要用完成时。答案就是C了

consider 的用法是consider to do
所以只能从B C 中选一
“lamp”（灯）的发明是过去的事情因而用不定式的完成时表示
即：was considered to have invented

有三个知识点：
1,do you think这里视为插入语,也就是说做题的时候不予考虑其对句子的影响,因此这句话实际上是Who was generally considered （ ）the lamps?
2,consider的用法：
consider sb.to do是认为某人做某事的意思.
例:China is considered to be one of the greatest country in the world.中国被认为是世界上最伟大的国家之一.
consider doing 是考虑的意思.
例I am considering going or not.我正在考虑去不去.
注意到题中who was considered,这是明显的被动形态,OK,这句话的意思也是再问谁被大家认为发明了灯泡?因此排除了A和D
3,不定式的一般时to do和完成时to have done的区别：
to do强调了一般时态,现在的和打算的概念；而to have done强调了完成的,过去的概念.本题中的电灯显然是过去发明的,因此要选择C.