根据句子意思，用括号中所给词的正确形式填空，每空填一词。
1. Three ______ (four) of the students in our class have handed in their reports.
2. You needn't be frightened because these insects are completely ______ (harm).
3. If you add some lemonade and sugar, the dish will be much ______ (taste).
4. How ______ (active) they are donating money to help the sick student!
5. Some of the film stars had been ______ (sing) before they entered the film industry.
