This excerpt from Mother Tongue clearly shows that: Nonstandard forms of English can be as effective as the standard form of English.
When the narrator uses the words "impeccable" and "broken" altogether, so as to catch the readers' attention, she suggests that although the mother has a fragmented and nonstandard English, she manages to make herself pretty clear when communicating something, not through her limited English, but by means of attitude: Tan's mother was very smart and understood very complex matters, such as listening to the Wall Street Week.
Regarding the other options, they are contradictory to what the excerpt really means. It is clear that although her English is limited, she still could stand for herself.
Nonstandard forms of English not necessarily make communication difficult between cultures, as seen in the excerpt's situation between Tan's mother and her boss.
The last option is not reflected in the given excerpt.
