她是位优秀的老师——她真的很在行。

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

她确实很在行。

She ___knew ___her ___stuff all right.

作为一名经验丰富的程序员，他真的很在行。

As a seasoned programmer, he really ___knows ___his ___stuff.