Final answer:
Since the question does not specify the expressions, it is not possible to determine how many of them have a-b as a factor; therefore, the answer is it depends on the values of a and b.
Step-by-step explanation:
The question posed is whether the expression a-b is a factor of a given set of options without providing specific expressions or polynomials. In this case, the answer choice is D. It depends on the values of a and b. Without knowing the specific values or expressions in question, we cannot definitively say that a-b is a factor of any number of them, as it would be contingent on whether the expressions can be factored to include a-b in their factors list.