砂型舂得太松，铸件容易产生（）缺陷。
A.气孔
B.胀砂
C.缩孔
D.加渣
参考答案：B
Which is wrong?[ ]
A. At Christmas, people eat dumplings.
B. At Christmas, people sing special songs.
C. At Christmas, children don't go to school.
偏头痛的先兆期相当于（）
A.颅内、外血管的扩张期
B.颅内、外血管的收缩期
C.颅外血管的扩张期
D.颅内血管的扩张期
E.颅内血管的收缩期
