No botanist lives long enough to study the complete life cycle of an individual California redwood tree. Nevertheless, by observing many trees at different stages, botanists can piece together the evolution of a single tree. Exactly the same principle applies in astronomy to the study of the life story of globular clusters, huge spherical aggregations of about a million stars all swarming about each other.
Which of the following is an assumption made in the passage above?
答案：C