Final answer:
Jun knew the meaning of 'escritoire' because he learned French from his grandparents and was able to translate the word into English. So thhe correct answer is Option D,
Step-by-step explanation:
The character Jun figured out what escritoire meant through his knowledge of the French language, which he learned from his grandparents. He did not need to look up the word in the dictionary, unscramble the letters, or call anybody for help. Therefore, the correct option describing how Jun knew the meaning of escritoire is that he changed the word into English based on his existing language knowledge.