Q: The main components of the circulatory system are the heart, blood vessels, and what else?


Read this paragraph and choose the correct option from the provided answers:

The circulatory system can be compared to a system of interconnected, one-way roads that range from superhighways to back alleys. Like a network of roads, the job of the circulatory system is to allow the transport of materials from one place to another. As described in Figure below , the materials carried by the circulatory system include hormones, oxygen, cellular wastes, and nutrients from digested food. Transport of all these materials is necessary to maintain homeostasis of the body. The main components of the circulatory system are the heart, blood vessels, and blood.

 Choices:

- lungs

- nerves

- brain

- blood


A:
blood