As a person exercises, carbon dioxide (co2) levels in the blood increase. this causes the nervous system to signal which of these systems to respond? a digestive and immune b immune and respiratory c respiratory and circulatory d circulatory and endocrine

It would be the equator

They use the si unit, or metric system its all the same thing

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on