根据括号中的要求改写下列句子。

1.We went to the post office to send a letter.(改为一般疑问句)

          you          to the post office to send a letter?

2.The pandas need to eat bamboos.(对画线部分提问)

                  the pandas need to eat?

3.It's important to learn English well.(改为同义句)

        English well        very important.

4.There are some animals in danger.(改为否定句)

There                  animals in danger.

5.We mustn't pollute rivers.(改为祈使句)

                 rivers!