Choose the best answer: 1. Doctors __ an answer to AIDS yet. A. have found B. found C. haven t found D. hasn t 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. 5. Would you like __ to my party?