Answer: A
Step-by-step explanation:
A - keywords give different moods and can contribute to an informational sense or a narrative one
B - headings are like titles, they can be interpreted in several ways, for example, let's say a book (or essay/ heading) was named "Forests". It could be informing the reader about forests or entertaining them with a story about a magical forest.
C- look at the last explanation.
D- length, as long as it is over the minimum amount required, it does not matter