Answer:
Middle East Respiratory Syndrome
Explanation:
The second statement best explains the type of blood vessel and the function of these vessels' valves - <span>These are veins, which prevent the backflow of blood because the walls have little muscle to pump blood back to the heart.
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Veins are large blood vessels which carry blood back to the heart. <span>Veins have a system of valves to prevent back-flow.</span>
3 Positive reinforcement is most effective when it occurs immediately after the behavior. Reinforcement should be presented enthusiastically and should occur frequently. Deliver reinforcement quickly: A shorter time between a behavior and positive reinforcement makes a stronger connection between the two
The most common source of water contamination is: A. sewage.
