笔帽

zhè zhī bǐ de bǐ mào zài nǎ

这支笔的笔帽在哪？

Where's the top of this pen?

tā bǎ bǐ mào kòu zài le yuán zhū bǐ shang

他把笔帽扣在了圆珠笔上。

He snapped the cap on his ballpoint.