It was not until midnight _________ his father came back.
A.when
B.while
C.that
D.as
答案:C
MG600/1385-WD采煤机的型号含义是什么?
导线的比载是指()
A、导线单位长度的荷载
B、覆冰时导线单位长度的荷载
C、导线单位长度、单位截面积上的荷载
D、覆冰、有风时导线单位长度的荷载