对齿轮轮齿材料性能的基本要求是（）.。
A.齿面要硬，齿心要韧
B.齿面要硬，齿心要脆
C.齿面要软，齿心要脆
D.齿面要软，齿心要韧
参考答案：A
She likes _________ articles about films a lot.
A．seeing
B．watching
C．looking
D．reading
I was just going to cut my rose bushes but someone _____ it. Was it you? [ ]
A. has done
B. had done
C. would do
D. will do
