求按要求改写句子

1.The most important thing is to save lives.
2.A postman's duty is to delivers letters and newspapers.
3.My purpose is to point out the difficulties of the matter.

The most important thing is to save our lives.
The duty of a postman is to deliver letters and newspapers.
My purpose is to point out the difficulties of the matter.

one of the most important thing is to save lives
one of his duty is to deliver letters and newspapers
one of my purpose is to point out the difficulties of the matter