常把粉尘中游离的二氧化硅含量高于（）称为矽尘。
A.5%
B.3%
C.空气中粉尘高于5%
D.6%
参考答案：A
The careless driver is _______ for the traffic accident_______ yesterday.
A．to blame; happened
B．to blame; happening
C．to be blamed; happened
D．to be blamed; happening
李明同学带着20kg的一筐苹果去看望爷爷奶奶，这框苹果的重力是_____，重力的施力物体是_____．
