Explanation:

Let’s break down the options:

- Option 1: 1.0

This number is way too low. If every woman had just one child, the population would shrink fast. It doesn’t allow for both parents to be replaced.

- Option 2: 1.6

Still too low. The population would gradually decline since it’s below the replacement rate.

- Option 3: 2.1

Here’s the thing: This is the textbook replacement level for stable population in most developed countries. It covers replacing both parents and accounts for childhood mortality and people who don’t have kids.

- Option 4: 2.3

A bit higher than needed, but in countries with high child mortality, it’s closer to the mark. Still, 2.1 is the general global standard.