A student had medical testing and discovered that her white blood cell count is lower than normal. Which of her systems are most likely functioning improperly?
A. nervous and immune
O B. circulatory and urinary
O C. circulatory and immune
O D. nervous and respiratory

b

Explanation: Viral infections that momentarily impair the function of bone marrow are the most common cause of a reduced white blood cell count. Certain defects with impaired bone marrow activity that are present at birth (congenital). Diseases of the bone marrow, such as cancer.