The line in the above excerpt from Amy Tan's "Mother Tongue" that shows that Tan changes her language depending on the audience is:
“The talk was about my writing, my life, and my book, The Joy Luck Club, and it was going along well enough, until I remembered one major difference that made the whole talk sound wrong. My mother was in the room.”
Amy Tan's essay “Mother Tongue” is about the difficulties that a child has to face if it grows in a family in which its parents speak 'limited English.' Amy's mother was among such parent who was unable to speak fluent and proper English. It is through the language that the person is judged by others. Amy was brought up by her mother and because of this, her writing style was much influenced by the language spoken at her home. Her mother taught her that a person's perception of the world is influenced by the language spoken at home.