Answer:
You have the right answer, its B.
Explanation:
Answer:
Survey
Explanation:
Because if you think about it carefully you really cant observe it. Your main goal is to compare them and with that we need a survey to get the data from both sides. Leaving us with the Survey
I think its strain or sprained
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.
