White blood cells:

can be classified as granulocytes or agranulocytes

defend the body against bacteria and viruses

are also called leucocytes

all of the above

are also called leucocytes

Explanation:

Leukocytes, also known as white blood cells, are cells produced by the bone marrow that have the function of defending the body against disease, infections and allergies.

They are an important part of the immune system, and their count assesses the body's response to different diseases - especially those caused by viruses or bacteria -, HIV infection, and radiotherapy and chemotherapy treatments. The test can also identify various types of leukemia, as well as track bone marrow function.