Only when I left my parents for America ____ how much I loved them

Listen! Peter is singing in the classroom!—It _____ be him. He has gone back to his hometown.

We wouldn’t have had to be in such a hurry if we had known the meeting

He is a strict and kind teacher, ______ my son loves and respects.

Though they don’t live in the same city now, he manages to be informed ________ how Tony is getting along.[ ]