The infection-fighting cells that are produced by the immune system are manufactured in specific places around the body, for example, in the lymph nodes and the spleen. However, an infection can occur anywhere in the body. How do these infection-fighting cells manage to move around the body and get to the sites of infection? A. There are lymph nodes every few millimeters all over the body.

B. They are excreted and float freely around the body, hunting infections.

C. They are carried around the body in the circulatory system.

D. They are moved around the body as muscles squeeze against them.