正常人心率超过180次/分时心排血量减少的主要原因是
A.减慢射血期缩短
B.减慢充盈期缩短
C.等容收缩期缩短
D.心房收缩期缩短
E.快速充盈期缩短
参考答案:B
—Did you meet the pianist at the station?
—No,he__________by the time I__________there.
A.had left;got
B.has left;reached
C.was leaving;got
D.left;had got
A.4:1
B.1:
C.2:1
D.:1