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They carry oxygen to your entire body, and carry carbon dioxide away from your body to be exhaled.
Answer:
D.) Helpful variations allow individuals to survive and reproduce better than members who lack these variations.
Explanation:
Variation is one of among the principles of natural selection.
Variations occur naturally thereby favouring some individual groups over the other.
In the above example, the helpful variations naturally select the parents of the offsprings while the other members of the group are disadvantaged.
