Explanation:

Let’s break down the options:

- Option 1: Kandahar is a major city in Afghanistan, but it’s not the capital.

- Option 2: Kathmandu is the capital of Nepal, not Afghanistan.

- Option 3: Kabul is the capital of Afghanistan. This is the correct answer.

- Option 4: Karachi is a big city in Pakistan, not Afghanistan.

So, Kabul is absolutely the answer you want. It's not just the political center—it's also the largest city of Afghanistan, and where most government activity happens. The other options are important cities, but not the right capital for Afghanistan.