After two years' research，we now have a ________ better understanding of the disease.(2013·全国Ⅱ)

A．very

B．far

C．fairly

D．quite

患者，女，32岁。劳累后气促，咳嗽，水肿半年。年幼时曾有一次长期发热伴关节痛史。检查：心率120次/分，节律不齐，心尖区有舒张期杂音，双肺底湿啰音，肝肿大，心电图示房颤。应首先考虑的是

A．二尖瓣关闭不全

B．二尖瓣狭窄

C．主动脉瓣关闭不全

D．主动脉瓣狭窄

E．三尖瓣狭窄