The Smiths consider _____ a computer, which is commonly considered _____ a great help in their work and study.

A．to buy; to be

B．buying; to be

C．to buy; being

D．buying; being

下列心电图改变对诊断急性心肌梗死最有意义的是（）。

A.Q波>同导联R波1/3

B.T波倒置0.2mV

C.病理性Q波伴S-T段呈弓背向上型抬高，与T波形成单向曲线

D.频发室性早搏

E.T波异常高耸，呈帐篷形改变