## Core Concept
The question pertains to the concept of population growth rates, specifically the classification of growth rates into different categories based on their annual percentage. Understanding the different types of growth rates, such as exponential, linear, and logistic, is crucial in demography and epidemiology.

## Why the Correct Answer is Right
An annual growth rate of **20% or more** is often considered indicative of 'explosive' or rapid growth. This type of growth is characteristic of populations or phenomena that are increasing very quickly, often leading to significant changes in a short period. The exponential growth model is a classic representation of such rapid increases, where the rate of growth is proportional to the current population size.

## Why Each Wrong Option is Incorrect
* **Option A:** < 5% - This growth rate is considered low and does not reflect explosive growth. * **Option B:** 5-10% - This range represents a moderate growth rate, not explosive. * **Option D:** 10-15% - Although this is a higher growth rate, it is still not typically classified as 'explosive'. ## Clinical Pearl / High-Yield Fact A key point to remember is that explosive growth, often seen in outbreaks or epidemics, can quickly overwhelm healthcare systems. Rapid growth rates can also be seen in certain types of cancer or in populations experiencing sudden demographic shifts. ## Correct Answer: C. 20% or more.