铸造过程中，液态合金从坩埚到被铸入铸型腔内的时间为
A．1/4～1/3s
B．1/2～1s
C．1～2s
D．3～4s
E．4～5s
参考答案：A
The role change of husband to father, although difficult, doesn't seem so great as _____ of wife to
mother. [ ]
A. that
B. one
C. this
D. those
水烧开时，壶嘴冒出许多“白气”，这些“白气”是[ ]
A．水蒸气
B．小水珠
C．热空气
D．白烟
