Which describes how blood can be protective in nature? by forming a protective layer within blood vessels by carrying cells that defend the body from foreign materials by secreting oil that destroys foreign materials by producing acid that kills foreign materials

The appropriate answer is B. by carrying cells that defend the body from foreign materials. These specialized blood cells, known as white blood cells or leukocytes, are the back bone of the body's immune system.
There are five types of white blood cells and they carry out different functions in order to defend the body against pathogens. Some of the functions include releasing enzymes that weaken parasites, destroying cancer cells and secreting antibodies.