二尖瓣狭窄最早出现的症状是()
A.水肿
B.咯血
C.劳力性呼吸困难
D.咳嗽
E.端坐呼吸
参考答案:C
用所给词的适当形式填空。
1. There are a few _______ (tomato) in the bowl.
2. _______ (not run) in the street!
3. The stars in the sky are _______ (count).
4. Let's _______ (sit) here and _______ (watch) TV.
5. The boy is _______ (put) his books on the bookshelf.
置换固溶体的溶解度与原子尺寸因素、()、电子浓度因素和()有关。