---Did you talk back to your mother when you were a child?---Yes. But now I realize I was wrong. I really regret ___________that silly thing to my mum.
—Do you know if Tom ________to the concert? — I’m not sure, but if he________, I’ll go to the concert with you.
At the party, she ________a ghost.
He found_ ________very difficult ________the math problem.
— What did Tina say? — Sorry, I didn’t ________ what she said.
—Do you know _____ ? I'm going to see him. —Sorry, I don't know.