Final answer:
The mother's statement that indicates a need for further instruction is option a because it suggests exposing the child to potentially crowded and germy environments shortly after cardiac surgery.
Step-by-step explanation:
The answer to the question is option a. "We are going to her cousin's birthday party tomorrow! The whole family will be there!" This statement indicates a need for further instruction because it suggests that the mother is planning to expose the child to potentially crowded and germy environments shortly after cardiac surgery. After surgery, it is important to minimize the risk of infection by avoiding crowded places and maintaining good hygiene practices.