黑白电视机图象信号的频带宽度是()。
A、6MHz
B、38MHz
C、31.5MHz
D、10.7MHz
参考答案:A
慢性心脏病患者心衰的最常见诱因是()
A.严重贫血
B.肺部感染
C.劳累
D.进食不当
E.情绪激动
I like the car very much, _____ it's too expensive for me. [ ]
A. and
B. so
C. or
D. but