电暖器的电热元件分为()几种。
A.电阻式电热元件
B.远红外线电热元件
C.PTC电热元件
D.燃气电热元件
参考答案:A, B, C
—I called you at 6 o'clock yesterday evening, but nobody answered.
—I'm sorry. I _______ my friend download the movie Kung Fu Panda Ⅱwhen the telephone rang, [ ]
A. would help
B. helped
C. was helping
每次接通汽车起动机时间不得超过5s。