铸件产生粘砂的主要原因是()
A.型砂强度不够
B.春砂太紧
C.浇注温度过高和造型材料耐火性差
参考答案:A
When he came in, I happened ___ on the bed ____.
A.lying; and read
B.to lie; reading
C.to be lying; reading
D.to have lain; reading
《素问·举痛论》指出:"悲则"()
A.气下
B.气消
C.气缓
D.气收
E.气结