单项选择题引起左心室后负荷增加的因素是（ ） A. 二尖瓣狭窄 B. 高血压 C. 肺动脉瓣狭窄 D. 二尖瓣关闭不全 E. 主动脉瓣关闭不全
多项选择题For contrasting ideas, expressions like ( ) are often used. A. However,... B. Nevertheless,... C. Although... D. Both...and...
