用单词的正确形式填空

1. He happened            __  __(help) an old woman on his way home.

2. I have forgotten____(return) his money, so he didn't receive.

3. I spent about half an hour in____(write) yesterday's diary.

4. She was very busy, so I let her____(go) back first.

5. At least we can afford         ____(buy) an electric bike.

6. I had something to ask him, but he avoided___    ( answer) my question.