It would be d because a cell is least complex and organ system is most complex
The outward appearance of a trait is called a phenotype.
The phenotype of the organism can differ from the genotype(genetic makeup of a trait). This can happen if one half of the trait is dominant over the other half, creating the trait the dominant side 'codes' for.
Answer:b) The air at high altitudes are less dense, so its harder to breathe.
Explanation:
AS altitude increases, the air pressure drops. This reduces the amount of gas molecules in the air so the air becomes less dense compared to air closer to sea level.