What is the purpose of the comma in a sentence?

What textual evidence in “all the lovely stars” indicates that christina regretted her initial response to her mother’s plan togo to arizona for spring break? a.)christina builds a miniature desert in an old aquarium for mother. b.)christina squeezed her mother’s hand when she got home from school. c.)christina was worried when she learned that her mother’s ankle was broken. d.)christina knows her mother is concerned about her well-being while she is at the hospital.