The soldier wrote a letter.
It's 2 because hers' means possessive and it's saying the book is his/her it's hers'
The answer is: support sentence.
Support sentences form the body of a paragraph. They provide facts and examples to develop the idea of the topic sentence. In the excerpt, the support sentences supply information about the koala "bear." For example, they describe, among other things, the kind of animal it is and its physical appearance.