The best way to punctuate the bolded portion of the quotation is the following:
C. them."-C.S. Lewis
This is the best way considering that the sentence ends on 'Lewis'. Periods always go inside quotations, as you can see from this brief description between different citing standards.
MLA: Commas and periods directly following quotations always go inside closing quotation marks. Question marks can vary depending if the question is part of the quote, then the punctuation mark goes inside the quotation marks. If the question is not part of the direct quote, it goes outside.
AP: All punctuation goes inside the closing quotation marks. This includes commas, periods, question marks and exclamation points.
Chicago: Periods and commas always go inside quotation marks. Question marks and exclamation points that are part of the original quote are included inside quotation marks.
