Both B and D use "publish" instead of published which is not on the correct tense, so we can rule those out. Then, I looked for another error, and you need an a before "patent clerk." So A, the other viable answer, was ruled out. C is correct.
Assuming that this is referring to the same paragraph that was posted before with this question, the best option would be "<span>b. He hides behind a tree" since this provides cover. </span>
