The correct option is C.
A plateau period refers to a period of time in which there is little or no growth or decline, everything is just stagnant. Looking at the sentence given in option C, it can be seen that the person been talked about is tired of his current position, which means that, he has been in the same position for a very long time; that is career stagnancy.
Based on the given excerpt above from “Like Mexicans,” the statement that best explains how Soto's text structure helps establish his voice in the excerpt is this: <span>Soto relates a story from his life to make a point about what it means to live in a multicultural society. The answer would be option C. Hope this helps.</span>
