绵马贯众具有驱虫与抗肿瘤作用的有效成分主要是（）
A.间苯三酚类化合物
B.挥发油
C.鞣质
D.树脂
E.生物碱
参考答案：A
He is busy. He keeps ____ these days.[ ]
A．work
B．to work
C．works
D．working
Nobody knew that the reason______ he was often blamed. Perhaps that was______ he made the same mistakes told several times.
A．which; because
B．why; because
C．that; that
D．why; that
