Answer:
18. The answer is terms and phrases that are intended to keep important information secret.
I think the topic sentence is sentence 10.
Answer: C. the introductory paragraph
Explanation: A thesis is a theory or an idea that the author expresses as a statement and then discussed it using logical arguments. When structuring an argument the thesis is the most important element because it expresses our point of view about the subject, and also represents the statement that must be refuted or approved, so, it must be in the introductory paragraph because it is the base of the following arguments we are going to write.
A- He believes that, in life, every individual must confront fear in some form or another.