The correct answer is B. Insert a colon between causes and an.
Explanation:
In writing, the colon (:) is a punctuation mark that introduces a list of items. Additionally, a colon should be used only if the sentence right before the colon is complete as otherwise it should be omitted.
In the case of the sentence presented the elements "an increase in the minimum wage, health care reform, and immigration reform" are a set of elements in a list that explain the various campaigns of Kennedy. Therefore a colon should be used to introduce this list especially because the first sentence is complete and there is not a transition to list the causes. Thus, in this sentence, you should insert a colon between causes and an, which means "Ted Kennedy championed various causes: an increase in the minimum wage, health care reform, and immigration reform".
