按要求变换句型。

1. We had a great time in Hong Kong last summer. (改为同义句)

    We _____ _____ in Hong Kong last summer.

2. To understand what he is saying is too difficult. (同义句)

    _____ _____ too difficult to understand what he is saying.

3. The children have never seen an Indian film, _____ _____? (完成反意疑问句)

4. He says the bus has already gone. (把主句变为一般过去时态)

    He _____ the bus _____ already gone.

5. Chinese people invented the abacus in the sixth century. (改为被动语态)

   The abacus _____ _____ in the sixth century _____ Chinese people.