In winter, we must pay attention to _________.

A．keep warm

B．keep warmly

C．keeping warm

D．keeping warmly

低血钾的典型心电图表现为（）。

A.QT间期延长

B.QRS波增宽

C.u波倒置

D.ST段压低，T波低平及u波增高

E.T波倒置