Answer:
It supports the idea that people judged the author's mother based on her language.
Step-by-step explanation:
The excerpt states that the narrator had to talk on the phone for her mother. The narrator proceeds to recount a time she spoke to a stockbroker in place of her mother. The stockbroker had attempted to scam the mother by not sending her check, presumably because they believed she would be easy to cheat (due to her less understanding of English).
By describing how the narrator had to speak for her mother because of skirmishes that occurred due to language complications, the author develops the idea that people assumed things about the narrator's mother and her abilities simply because she had less fluency in English. They believed that, since she did not speak English very well, she would be easier to trick, implying they thought her to be incapable and/or intelligent.
This answer choice also matches the theme that "one's skill in language does not prove/measure their capability and intelligence." The other answer choices do not reflect this theme as efficiently.