13. Children shouldn’t waste time _______ in front of a computer all day. A. sit B. to sit C. sitting D. to sitting 14. We see a strange ship ______ by computers in our sea. A. is controlling B. to control C. controlled D. controlling 15. One of _____ way to study a subject well is our love for it. A. the most suitable B. most suitable C. suitable D. the best suitable 1. Unless she (try) __________________________ harder, she can’t pass her final exam. 2. As he (practice) __________________________ his piano lesson, some friends came over to see him. 3. Mary or her classmates (do) ________________ the class duty every day. 4. What we need to do now is (find out) ____________________ a cure for the pandemic.