He never speaks to others until ______.
Boris has brains. In fact, I doubt whether anyone in the class has___IQ.
Professor White has written some short stories, but he is___known for his plays.
—— Have you seen___pen? I left it here this morning. —— Is it___black one? I think I saw it somewhere.
Many people agree that___knowledge of English is a must in___international trade today.
How beautifully she sings! I have never heard____.