Ron is an avid reader. He has a large vocabulary because every time he comes across a word he doesn't know, he looks it up in the dictionary. Ron encounters "wanderlust" in a novel, reaches for the dictionary, and finds out this word means "desire to travel." The process of looking up unfamiliar words increases Ron's . a. lexicon b. parser c. syntactical capacity d. mental set

The process of looking up unfamiliar words increases Ron's a. lexicon.

Explanation:

Lexicon is a synonym for vocabulary, that is, all the words used by a person. When someone like Ron looks up unfamiliar words, he is enhancing, increasing, his vocabulary - the number of words he understands and is, therefore, able to use. Now that he knows what "wanderlust" means, that word has become a part of Ron's lexicon.