On weekends he usually has time to spend his son. [ ]
A.at
B.for
C.with
D.in
答案:C
船舶的肋骨或纵骨间距一般不大于()。
A.500mm
B.550mm
C.600mm
D.650mm
()新产品定型由国务院计量行政部门授权的技术机构进行;样机试验工作由当地省级人民政府计量行政部门授权的技术机构进行。