Of the choices that are given here, the best answer is C.
First, we can say right off the bat that D cannot possibly be the correct answer. When you are taking a multiple choice test, you should look for things like this where two of the options contradict one another. When they do so, you can eliminate “all of the above” as the answer. That means you only have to choose from three options and not four, thus improving your chances of getting the right answer. A and C cannot possibly both be true and therefore D is not right.
B is not correct either. First of all, Calhoun died a few months before Taylor did. In addition, he was not plotting to have the president of the United States killed. B implies that Taylor’s death was planned by Calhoun. This is not true.
The best answer is C. With Taylor’s death, Millard Fillmore became president. He had been in favor of coming to a compromise. Therefore, his becoming president helped to allow the passage of the Compromise of 1850. This means C is the best answer.