Check someone's understanding:
A: Do You understand of what se said?
B: Yes, she said that we should speak english in our english class.
A: Do you know i mean?
B: yes, sir
A: Do you understand the text?
B: i'm trying mam
A: Do you understand what the teacher ask to do?
B: We should use english in our english class.
Ask someone's attention:
A: Attention please, Attention!
B: yes, mam
A: Excuse me, mam . may i wash my hands?
B: yes, sure
A: Hey, let's go to the canteen
B: sure, let's go
A: Everybody, are you ready to learn English today?