What are the three main parts of the circulatory system

Explain how fossils scientists make discoveries about the lives of organisms and about how environments have changed over time. plz hurry up it time

The influenza virus cause the flu, but not other diseases. why?

The unique structure of the neuron is dedicated to the efficient and rapid transmission of neural signals. the relationship between neurons, the spinal cord, and the brain constitutes an elaborate communication system throughout the human body. all but one of the functions listed below are a result of this interaction.