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1. Doctors _____ an answer to AIDS yet. A. have found B. found C. havent found D. hasnt found 2. Do you mind _____ up? A. wash B. washing C. washed D. to wash. 3. He _____ to give up smoking since last week. A. was trying B. have tried C. has tried D. tried. 4. He enjoys _____ in the rain. A. walk B. walks C. to walk D. walking.