Answer: The right answer is “I thought C.S. Lewis wrote only children’s books," said Ryan — you are adding a comma and a quotation after <em>books</em>.
Explanation: Just to elaborate a little on the answer, it can be added that since the speaker is directly quoting Ryan's exact words, he or she is using quotation marks in order to identify them. In the United States, and if you follow the documentation style known as the APA style, the comma or period punctuation must be placed before the final quotation mark. For that reason, since the direct quotation ends in the word "books," the comma and the quotation must be placed after it.
While I <u>was taking</u> a shower, my cell phone rang. I asked my sister to answer it, but she didn’t hear me because she <u>was cleaning</u> the backyard.
