下列物体属于助燃物的是（）。
A、氧气
B、木柴
C、煤炭
D、油页岩
参考答案：A
It is said that potato chips in KFC _____ by mistake about one hundred years ago. [ ]
A. were invented
B. invented
C. was invented
无压引水式电站沿水流方向主要流经的建筑物有（）。
A.无压进水口
B.明渠或无压隧洞
C.压力前池、压力管道
D.厂房、尾水渠
