After a hard ---fought campaign, Barack Obama won the US presidential election, and became

President of the United States---the first African –American in           

country’s history to do so.

A．the; the

B．/; /

C．/; the

D．the; /

下列不符合三度房室传导阻滞心电图表现的是（）

A.P波与QRS波群无关

B.R波频率大于P波频率

C.R-R间距相等

D.P-P间距相等

E.心室率多在30～40次/分