He often ________books ________the library．

It’s your decision — you must ____ the responsibility if things go wrong.

Excuse me. Which is the way ______ the post office, please? —Sorry, I don’t know. You can ask the policeman _______ help. [ ]

You can never imagine the great difficulty I had ______ her QQ number.

The man in a black suit _______ be our youth worker. — I’m sure it _____ be him. I saw him in the laboratory building some minutes ago.