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.
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A. to be; have fallen B. to have been; to have fallen C. to be; to fall D. having been; having fallen
---What would you like ______ this Sunday? How about hiking in he mountains? ---I don’t feel like ______in the mountains. I like ______ something else.
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A.doing; hiking; doing B. to do; to hike; to do C. to do; hiking ; to do D. doing; to hike; to do