我无法入睡，因为这个问题一直在我脑海里盘旋。

I couldn't sleep because the problem was going round in my ___head.

一个绝妙的主意突然冒了出来。

A brilliant idea suddenly popped into my ___head.

然后那个想法突然出现在我脑海中。

Then suddenly the idea came into my ___head.