The wreckage of something like a jet plain discovered in the heart of the desert is believed ______ a UFO and _______down for reasons still mysterious.
Rose, don’t pick the flowers in the park, _______?
Every second counts in the exam, _________ means you must make the best use of the time available.
John isn’t here right now. He ______ Mr. Black’s office. Perhaps he______ in several minutes.
It is said that the second book __________ is written by the singer hasn’t come out yet.
— Dad, would you please buy some strawberries for me? I love them. — I'd like to, but they are not _____ in winter.