Which of these is an example of a plateau period? a. a community group invites you to become a member. b. you take up a sport you've always been interested in and learn how to play it quickly. c. you recently received a good review from your boss, but you're tired of your current position. d. you're excited about starting a new job, but also a bit nervous.

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.

Writing since he was a writer

Aparagraph would strengthen it the most