用所给动词的适当形式填空。

1. We want to invite our classmates _________ (have) a picnic tomorrow.

2. —Millie, please tell your brother not to cross the road, it is dangerous.

    —Thank you, I __________ (ask) him to be careful.

3. One of the red key rings__________ (belong) to Millie.

4. Why not __________ (visit) the Great Green Wall next month?

5. He is looking forward to __________ (spend) his holiday in Shanghai next month.

6. Can your sister __________ (sing) the song in English?