This assignment is going to require you to take some preliminary steps before this question can be fully answered. First, you must choose a theme subject presented in the novel. Some theme subject examples from this novel include: identity, especially the difference in cultural identity between the Chinese mothers and their Chinese-American daughters; conflict, choices, and consequences; mother-daughter relationships.
Once you have chosen a theme subject, create an open-ended question and jot notes as you read which will help answer this question. An example question might be: "What overall message is the author trying to convey about this subject through the characters and plot details in the story?" Take notes by paraphrasing examples as well as including some quoted material. Once you've gathered several examples, read through them and use them to create a broad statement which answers your open-ended question. (This sentence, sometimes called a "theme statement" will become the thesis for your essay.)
Once you have created a theme statement (which can be a work in progress), organize your examples into logical categories. If you are required to come up with four specific examples, a logical breakdown, for this story, is to focus on one example from each mother/daughter pair in the novel.
The link below may help you in the preliminary brainstorming and deciding on a particular theme subject to follow. Once you've made that decision, feel free to come back to Enotes to ask for more specific help and ideas pertaining to your essay.