Answer: D) “Now many people use low-calorie sugar substitutes to control their weight” (Kowalsky 19).
Step-by-step explanation: when quoting a source in a paper or an essay, we need to cite that source in the correct way. According to MLA the format to write a parenthetical cite is to write the last name of the author of the source (book, article, etc.) followed by the number of the page from which we got the quote, this two elements must be in parentheses, and if it is the end of a sentence or a paragraph, the period must be after the last parentheses, also the cite isn't part of the quotation, so it must not be included in the quotation marks. The option that follows this format correctly is “Now many people use low-calorie sugar substitutes to control their weight” (Kowalsky 19).