D is your answer
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Answer:
it is the change in one or more genes
Answer:
Option a) higher the average sea levels.
Explanation: Carbondioxide is also known as greenhouse gas. When carbondioxide concentration is higher in the atmosphere, it prevents the reflected sunlight from going into the atmosphere which increases the temperature of the surrounding air. This phenomenon is called global warming. This increase in temperature starts melting of ice which are present on mountains and thus, increases sea level.
As any other ancient civilization, the Sumerians were traders as well. And they had a few good reasons to do this.
Because they traded, their trading partners were less likely to attack them, because it would hurt their economy as well. Furthermore, they didn't produce everything they needed and traded those goods with goods which they produced too much of.
And lastly, through trade they could also get exotic goods which they would have never gotten otherwise.
Answer: Possession of Valves
Explanation: Veins possess valves which ensures that blood flows in only one direction. Valves helps blood to flow back to the heart against gravitational force.
Arteries don't have valves because the pressure originating from the heart is capable of causing the blood to flow in one direction.