在生产矿井中主要运输线路(大巷、井底车场、斜井、地面干线)•轨型不得低于()
A.18Kg/m
B.22Kg/m
C.30Kg/m
参考答案:B
They do eye exercises twice a day , so ____of them ____glasses.
A.few, put on
B.few , wear
C.a few , put on
D.a few, wear
计算a3•a4的结果是( )
A.a6
B.a7
C.a8
D.a12