IS06871标准中要求钴-铬和镍-铬铸造合金中铬含量不得低于（）
A.10%
B.20%
C.30%
D.40%
参考答案：B
风吹着帆船航行，说明风具有______能；急流能把石头冲走，说明水具有______能．
_____ received law degrees as today. [ ]
A. Never so many women have
B. Never have so many women
C. The women aren't ever
D. Women who have never
