她是位优秀的老师；她真的精通本行。

She's an excellent teacher; she really ___knows ___her ___stuff.

在汽车维修方面，你可以相信他的建议；他对此非常在行。

You can trust his advice on car repairs; he really ___knows ___his ___stuff.

我们聘请的技术顾问对他的领域了如指掌。

The technical consultant we hired ___knows ___his ___stuff inside out.