Houston Rockets, ______ led by as many as 10 points in the first half, has dropped three straight after winning eight matches.

A．which

B．that

C．it

D．when

患者，男性，54岁，劳累后感心悸。查脉搏，每隔两个正常搏动后出现1次过早的搏动。判断此脉律为

A．二联律
B．三联律
C．频发期前收缩
D．成对期前收缩
E．脉搏短绌