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!?