能与水中溶解氧发生氧化－还原反应是（）除氧的原理。
A、热力除氧
B、真空除氧
C、电解除氧
D、亚硫酸钠除氧
参考答案：D
If there were no exams and parents meetings, high school life __ much enjoyable.
A．will be
B．must be
C．would be
D．would have been
代表心房除极波形的是：（）
A.P波
B.QRS波群
C.S-T段
D.T波
E.Q-T间期
