Final answer:
4) Granulocytes are the white blood cells always containing granules and referred to as polymorphonuclear leukocytes. Hence, 4) is correct.
Step-by-step explanation:
The type of white blood cells that always contain granules and are commonly referred to as polymorphonuclear leukocytes are granulocytes. Granulocytes include three types: neutrophils, eosinophils, and basophils.
These cells are called granulocytes because they contain abundant granules within their cytoplasm. They play a crucial role in the body's immune response by defending against bacteria and viruses.