问题补充：
It is said that potato chips by mistake about a hundred years ago.
A. invent
B. invented
C. are invented
D. were invented
答案：
A. invent
B. invented
C. are invented
(答案→)D. were invented
解析：考察时态及语态。句意；据说炸薯片是100年前错误的被发明的。结合语境可知本句描述的是过去的状态，故用一般过去时态。句子主语是动作对象，故用被动语态。选D。
