—I apologize to you for my rudeness yesterday, Mary? —Never mind, and I think ______ of it.

. --- Sarah said she wrote you a letter. --- I wonder ______ she is writing to me about.

The information he gave us was quite different from _______ we got ourselves.

David said that it was because of his strong interest in literature ___ he chose the course.

Listen! ________ is knocking on the door. Go and see who it is.