Answer: pragmatics
Explanation:
Pragmatics simply means the study of how words are used. It's the study of signs and symbols. Pragmatics includes speech acts, implicature, and conversation.
Since Richard, a sixth-grader, uses codes such as LOL, TTYL, and 411 in his text messages, then the use of these codes in this context indicates that Ricard understands pragmatics.
