Formal.
As far as I know, there is no such thing as either standard or practiced diction. Informal is the way you communicate with your friends, for instance, which is not how you would write a thesis paper, legal document, etc.
Why would you need someone to do an narrative for you
Turtles spend most of their lives in water. They are adapted for aquatic life, with webbed feet or flippers and a streamlined body. Sea turtles rarely leave the ocean, except to lay eggs in the sand. Freshwater turtles live in ponds and lakes, and they climb out of the water onto logs or rocks to bask in the warm sun.
Each child was allowed to pick out <u>his or her</u> clothes for the day.
Hope this helps. :)
