一般用于传动的螺纹是（）螺纹。
A.三角形
B.梯形
C.锯齿形
D.矩形
参考答案：B, C, D
Faced with the ________ result, Chinese football fans took on ______ expression.
[ ]
A. disappointing, disappointing
B. disappointed, disappointed
C. disappointing, disappointed
D. disappointed, disappointing
I think maths is ________ than Chinese.
A．more difficult
B．difficult
C．hard
D．easy
