The sentence which most improve the sentence by adding description is this: 'there are plenty of vegetables, flowers, and plants at the community garden where I work. This sentence is descriptive in nature and tell us some of the charactersitics of the place where the speaker works.
I believe the answer to your question is B. Conflict
I would say the answer is A
Yes, you can say that! Or you can say “letter that contains advice” or “letter that provides advice.”