The life cycle of stars is on the order of billions of years, much lon

OFFICIAL EXPLANATION

Basically what the passage is saying is that humans are intelligent enough to understand the life cycles of stars, simply by grouping stars by their age and seeing what the various types of stars look like at different ages. To demonstrate how amazing this is, the passage ends by asking you to imagine that a mayfly, which lives for just one day, can understand the human lifespan by doing… something. Among the answer choices, what is the best analogy? What could an intelligent mayfly do that would be similar to the human grouping of stars by their ages and stages of life?

(C) is the best answer, because it suggests a college reunion with multiple graduating classes that are five years apart. There would be groups of 27-year olds (young adulthood), 32-year olds (early middle age), 37-year olds (middle age), 42-year olds (later middle age), and so on, conceivably all the way up to groups of people in their mid-70s, early 80s, perhaps even 90s. So we have groups of people at discernibly different stages in their lifespan, analogous to groups of stars at different stages.

(A) doesn’t work as well as C, because it only involves humans in two stages of life: childhood and adolescence. This doesn’t capture nearly as many groupings of the human lifespan. Not only that, but if the K-12 school is a one-room schoolhouse, Montessori school or some other alternative school, the students might not even be grouped by age at all.

(B), like A, represents two stages of life only. Not only that, but B strongly suggests the two age groups, grandparents and grandchildren, would be mingled and interacting, not separated apart by age.

(D) mentions only one person seen in many stages of life, not groups of people who are in different life stages. Since the passage mentions groupings of stars and not just one individual star, D is not the comparison we’re looking for.

(E) describes a hospital that is full of humans from all stages of life, just as the Hertzsprung-Russell diagram is full of stars from all stages of life. However, this is still not as good of an analogy as C. In the HR diagram, the stars are actually grouped together by life stage. However, in a hospital, humans aren’t generally grouped by life stage. You could easily have a 20 year old in a hospital bed next to a 60-year old, and a pediatric ward might intermingle toddlers, children, and adolescents.