该特工被派往国外，负责对军事设施进行间谍活动。

The agent was sent abroad to ___spy on military installations.

该软件旨在防止竞争对手窥探我们的研究。

The software is designed to prevent competitors from ___spying on our research.

我觉得我弟弟在试图打探妈妈把我们的礼物藏哪儿了。

I think my little brother is trying to ___spy on where Mom hid our presents.