In which situation is the same time period necessary for a correct comparison of growth rates?

Correct answer: While comparing the growth rates of two areas

Direct answer: Option A. A growth rate measures change in relation to a specified period, such as one year, five years, or one decade. To compare two areas fairly, both rates should refer to the same length of time and, where relevant, the same unit such as percent per year. If one area is measured over one year and another over ten years, their figures may not be directly comparable; the apparent difference could result from the different periods rather than from a genuine difference in growth. Option A is correct because it involves comparing demographic rates. Option B is wrong because measuring river length is a distance task, not a comparison of population-growth rates. Option C is unrelated to a rate. Option D concerns colour and has no time-based demographic measure. Memory cue: compare like with like—same areas, same units, and same time period.