Answer:
Explanation: what is a relay race? A relay race is a competition, of different type of stuff, like running qartwheels . The caterpillar, and man more. Hope this helps
The answer is c.
hope i helped
Answer:
the last choice.
Explanation:
veins have valves because venous pressure is often not great enough( as the blood must overcome gravity and other forces) to return the blood to the heart.
valves mainly prevent the back flow of blood.