一般要求高炉煤气的含尘量≤()mg/Nm3。
A.80
B.20
C.40
D.10
参考答案:D
.
By around 900 AD,there were many places in Northern Europe______the Vikings chose to live.
A.in which
B.when
C.which
D.at which
硅酸盐水泥的初凝时间不小于( )min,终凝时间不得超过( )min。
A.30,100B.45,390C.40,600D.90,720