第一次闻雷表明雷暴云顶出现冰晶化现象，据此可以判断云顶已达（）等温线高度附近。
A.-5℃
B.-10℃
C.-15℃
D.-20℃
参考答案：D
甲数=a×b×b×c，乙数=a×b×d（a、b、c、d都是质因数），甲数和乙数的最小公倍数是______．
—Where did you see him for the first time?
— It was in the factory _________ we worked.
A．that
B．where
C．which
D．when
