stuff ·phrase (IDIOM)
Definition: to know a lot about a subject, or to be very good at doing something Level: C2
她是位出色的老师——她确实很精通自己的专业领域。
She's an excellent teacher - she really ___knows ___her ___stuff.
她从不怀疑自己的能力。她确实非常内行。
She never doubted her own abilities. She ___knew ___her ___stuff all right.
让他看看代码吧；在编程方面他真的很在行。
Ask him to look at the code; he really ___knows ___his ___stuff when it comes to programming.