我在浴室发现了一只蟑螂，赶紧拿杀虫剂喷它。

I found a ___roach in the bathroom and quickly sprayed it with insecticide.

他把抽完的蟑螂（指烟蒂）放在烟灰缸里。

He put the ___roach in the ashtray after smoking.

这条河里有很多蟑螂。

This river is full of ___roaches.