二尖瓣脱垂时心音可见（） ["收缩晚期喀喇音","收缩早期喀喇音","全收缩期杂音","收缩中期喀喇音","第二心音分裂增宽"]
二尖瓣关闭不全严重反流的体征可见（） ["心尖区第四心音和短促舒张期隆隆样杂音","心尖区第二心音和短促收缩期吹风样杂音","心尖区第三心音和短促收缩期吹风样杂音","心尖区第三心音和短促舒张期隆隆样杂音","心尖区第四心音和短促收缩期吹风样杂音"]
慢性二尖瓣关闭不全首先临床表现是（） ["水肿","疲乏无力","食欲不振","呼吸困难","心悸"]
二尖瓣关闭不全的瓣叶风湿性损害最为常见，约占（） ["2／3","1／4","2／5","1／5","1／3"]
有风湿活动的患者应长期甚至终身应用（） ["苯唑青霉素","氨苄青霉素","羧苄青霉素","磺苄青霉素","苄星青霉素"]
某套管内径φ120mm，外径φ152mm，问：该套管每千米的质量是多少？S＝（π／4）D2（不考虑接箍的质量）
