The answer is probably B because white blood cells are part of the immune system, so help to fight diseases. The circulatory system helps to move the white blood cell around the body. Also, pathogens are disease causing organisms, and as you can see, they all relate very well. Hope i helped, have a nice day.
Back in the 1800's. There were 2 variations of moths. 1 with white and 1 with black. The black colored moths could blend in the with the coal mines to hide from predators.
Anterior, middle, and posterior