Jack is late again. It is ___ of him to keep others waiting.
Every one of us must know:________we live can we save the earth.
—Can those________at the back of the classroom hear me?—No problem.
―Why? Where is my cellphone?―Dear me! You _______ it in the taxi!
You need some facts _____ to base your theory.
________ for not keeping his promise,Gary hung his head in shame.