三尖瓣狭窄可见()
A.右心室和肺动脉干扩大
B.左心房轻度增大伴明显肺淤血
C.右房和上腔静脉突出
D.左心房增大
E.右房增大,右心室上腔静脉和奇静脉扩大
参考答案:C
You _____ wash your hands before meals. It is good for your health. [ ]
A. may
B. can
C. have to
D. must
影响宽展的因素有哪些?