Christina owns and operates a shop that sells home furnishings. One of her vendors has just offered her a greatly reduced price for some traditional Christmas decorations, even though it is really too early to be thinking about holiday merchandise. One of the main pricing issues Christina will have to address as she considers the offer is

The claim.

Explanation:

Let's look at what the sentence does.

"Topic [x], [y], and [z] are factors of [z]."

This is not a reason, as it doesn't attempt to explain anything.

There is no proof in the sentence itself, so it cannot be evidence.

It does not counter a previously made argument, it just sets forth a new claim - so your answer is A. The statement is a claim.