How does this line relate to the artwork?

It points out that the artwork addresses a sad topic.
It explains the importance of light to supporting life.
It compares the painting to an emotional experience.
It suggests that the scene was painted at night.

The italicized noun clause is "what i like best about the farm."

B) Subject complement.

Explanation: A noun clause is a dependent clause that acts as a noun. Noun clauses begin with words such as how, that, what, whatever, etc. Noun clauses can act as subjects, subject complements, direct objects, indirect objects, predicate nominatives, or objects of a preposition. In the given sentence the noun clause is used as a subject complement because it is placed after a linking verb (to be) and it characterizes (or gives further information) about the subject (The fresh air).