基本语法 1. When it gets dark, the people ________ (set) off firecrackers. 2. They ________ (begin) to plant trees as soon as they get to the park. 3. She'll go shopping with me if she ________ (have) free time. 4. If he ________ (come) back,ask him to call me back. 5. He ________ (not come)if you don't invite him.