Tan uses the word “impeccable” to describe her mother's English.
Answer: D
Explanation
In the story, Tan describes her mother when she shouts a stockbroker's boss using in impeccable English.
This means that even though Tan's mother is not fluent in her English, he still believes that her English is still well enough.
Tan felt the band when he described his mother's English as broken.
This always bothered him and thought it was destroyed and was to be implemented since it lacked sound and wholeness.
Therefore this is the reason why he described it as impeccable.