The correct answer is A. I would help you with your math homework, but I have never been very good at math.
Explanation:
In grammar, a coordinating conjunction is one type of connection that links two ideas or elements that have the same level of importance this includes the conjunctions and, but, or also, this conjunctions differ from subordination conjunctions because subordinating conjunctions link ideas that do not have the same importance and from correlative conjunctions, because correlative conjunctions always come in pairs. Considering this, the sentence with a coordinating conjunction is "I would help you with your math homework, but I have never been very good at math" beecause, in this case, the conjunction is "but" which is a coordinating conjunction in most cases and also this word links two ideas with the same importance which the role of coordination conjunctions.
I would help you with your math homework, but I have never been very good at Math. It is the correct answer because It connects to two equal independent clauses whereby each can stand alone. For example I would help you with your Math homework. It barely stands alone. I have never been very good at work. It also stands alone.
