**Core Concept**
Doubling time is a measure of how long it takes for a population to double in size, assuming a constant annual growth rate. This concept is crucial in demography and population studies, where it's used to predict population growth and plan for future needs.

**Why the Correct Answer is Right**
The correct answer can be calculated using the rule of 72, which is a rough estimate of the doubling time of a population. The rule states that to find the doubling time, you divide 72 by the annual growth rate percentage. For a growth rate of 1.5%, the doubling time would be 72 ÷ 1.5 = 48 years. For a growth rate of 2%, the doubling time would be 72 ÷ 2 = 36 years. However, since the question asks for a range, the correct answer is 35-47 years, which is a reasonable estimate considering the range of growth rates provided.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option suggests a much longer doubling time than expected, which is unlikely given the growth rates provided.
* **Option C:** This option underestimates the doubling time for the lower growth rate and overestimates it for the higher growth rate.
* **Option D:** This option significantly underestimates the doubling time for both growth rates, making it an incorrect choice.

**Clinical Pearl / High-Yield Fact**
To quickly estimate the doubling time of a population, you can use the rule of 72. However, keep in mind that this is a rough estimate and actual doubling times may vary depending on various factors such as fertility rates, mortality rates, and migration patterns.

**✓ Correct Answer: B. 35-47 years**