How beautifully she sings! I have never heard＿＿＿＿．

A．the better voice

B．a good voice

C．the best voice

D．a better voice

肺动脉瓣狭窄指肺动脉瓣、瓣上或瓣下有狭窄，主要的病理生理改变为（）

A.右心室的排血量受阻

B.右心室压力增高

C.右心室代偿性肥厚

D.右心室失代偿性肥厚

E.右心室扩大以致衰竭