This paper investigates the ways readers use two semantic tools, synonymy and entailment, when responding to reading-comprehension questions. After a brief overview of semantic theory, two reading passages and their attendant multiple-choice questions are analyzed, demonstrating how readers might choose the correct answer by analyzing the way it paraphrases or entails material presented in the passages. The paper concludes that these semantic tools are useful to teachers, either in reading or in the content areas, who develop and test comprehension. (RL)