The answer is A, 'a mammal' because it goes with the copulative verb 'to be', i. e., 'is'.
Answer:
White
Immune
Explanation:
White blood cells, also called leukocytes, are one of the cells that are involved in the body's immune system. They protect the body against various infections diseases and other invaders. Leukocytes are produced in the bone marrow (hematopoietic stem cells). They are not the only cells that are important for the defense of the body but are important.
