On our arrival, we found Tom _____at the desk and ______a letter.
My parents would have come to see you if it had been possible, but they ________ so busy.
Mary is a(n) _______ customer, so the waiter knows her likes and dislikes.
Recently I bought a ticket for Shanghai World Expo, _______ was very reasonable.
—I’d like to call you at 10 o’clock next Friday morning if it is convenient.—I’m afraid I _______ an important meeting.
What some teenagers don’t realize is ____ difficult life can be if they get addicted to drugs.