Why does jean tell lin nai-nai not to use "sewing machine" as an english greeting at the end of the story. ( the story is homesick)

In Homesick: My Own Story by Jean Fritz  the reason why Jean tell Lin Nai-Nai not to use "sewing machine" as an English greeting at the end of the story is C: because he doesn't want Lin Nai-Nai to embarrass herself.

This fictionalized autobiography relates the story of a young girl ( the author) immigrating to China in the middle of political agitation. Lin Nai-Nai is her nanny and becomes an important support for her. This little girl notices that Ian Forbes, a villain according to the author's view, has tricked Lin Nai-Nai into saying something silly and tells her nanny right away since she is really fond of her and does not want to see her ridiculizing herself in public.

they used personification to make the truck seem mean and violent.

hope this !

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