Just my humble opinion, but I think it would be easier to learn the Thai characters if you used the standard Thai way of talking about individual characters and used a more standard transcription system. See the attached screenshot. Which choice is correct? Hard to know. But, if you used the standard way of talking about ท and called it ท ทหาร and transcribed it (for those who need it) as tho thahan it would be easier to learn and easier to figure out which answer is correct on the quizzes.