The correct option is B a
Let’s examine the sentence: “The main determination of economic success is our ability to control inflation.” The sentence wrongly uses “determination” to indicate factors of economic success. The word “determination” means “firm intention to do something.” The sentence should use “determinants” instead of “determination.” The word “determinant” means “determining agent or factor.” So, the error is in Part a of the sentence. Hence, Option A is the correct answer.