## **Core Concept**
The core concept being tested here is the **Rule of 70**, which is a formula used to estimate how long it will take for a quantity to double given a fixed annual growth rate. This rule is commonly applied in demography, finance, and biology.

## **Why the Correct Answer is Right**
The **Rule of 70** states that to find the number of years it takes for a quantity to double, you divide 70 by the annual growth rate (expressed as a percentage). Given an annual growth rate of 1.2%, we can calculate the doubling time as follows: 70 / 1.2 = 58.33 years. This matches option , which indicates approximately 58 years.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option suggests about 6 years, which would be incorrect because 70 / 12 = 5.83, not matching 1.2% growth rate.
- **Option B:** This option suggests about 12 years, which is also incorrect because 70 / 6 = 11.67, not relevant to a 1.2% growth rate.
- **Option D:** This option suggests about 600 years, which is far too long and incorrect because it doesn't align with the calculation for a 1.2% growth rate.

## **Clinical Pearl / High-Yield Fact**
A useful pearl to remember is the **Rule of 70**, which provides a quick method to estimate doubling time. For a 1% growth rate, the population doubles in about 70 years. This rule helps in understanding population dynamics and can be applied to various growth rates.

## **Correct Answer: .**