呼气性呼吸困难见于（）
A.急性喉炎
B.气管异物
C.阻塞性肺气肿
D.老年性肺气肿
E.肺不张
参考答案：C
—Why is ______ easy for such a young girl to learn three foreign languages so well?
—Because Britain, Germany and France are all very near ______ country. [ ]
A. it; his
B. that; his
C. she; her
D. it; her
在钢中加入Nb、V、Ti元素进行微合金化有什么作用？
