以下不属于合成毒品的是（）
A、摇头丸
B、海洛因
C、冰毒
D、K粉
参考答案：B
My friend told me it would be months _________ his family settled down in that city.
A．after
B．since
C．before
D．when
在一杯清水中，慢慢滴入几滴红墨水，过一会儿，清水渐渐变成红色，这是___________现象．
