Definition: to know a lot about a subject, or to be very good at doing something Level: C2
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.
