Nursing care of the child with myelosuppression from leukemia or chemotherapeutic agents should include using good hand washing technique to prevent infections. Option B is the correct answer.
Options A, C, and D are incorrect. Restricting oral fluids can lead to dehydration, which can exacerbate the child's condition. Immunizations are not recommended during myelosuppression, as the child's immune system is already weakened. Strict isolation with no visitors allowed can be emotionally distressing for the child and may not be necessary unless the child is experiencing severe neutropenia.