Explanation:

Let’s break down what’s going on here:

- The concept of alienation is most famously discussed by Karl Marx. He uses it to talk about how workers feel disconnected from their work, the products they make, and even from themselves under capitalism.

- Max Weber talks about bureaucracy and rationalization making people feel trapped (“the iron cage”), which is a sort of alienation, but the explicit term and systematic concept is Marx’s forte.

- Emile Durkheim deals more with ideas like “anomie” (normlessness), rather than alienation per se. They’re related, but not the same.

- Talcott Parsons doesn’t really mess with alienation much. He focuses on how different parts of society work together to keep things stable.

Now, the options:

- Option 1 (1,2): Says Marx and Weber talked about alienation. Weber’s take is debatable—his main themes aren’t alienation, even though there’s some overlap.

- Option 2 (3,4): Durkheim and Parsons? Not really.

- Option 3 (1,4): Marx and Parsons? Parsons didn’t work on alienation.

- Option 4 (2,3): Weber and Durkheim? As above—Weber touches on it, Durkheim doesn’t frame things this way.

Here’s the key: The central, systematic concept of alienation is really Marx’s. Weber circles around it, but he doesn’t develop it as a major concept.

So the best fit is that the concept has been elaborated and used in the writings of Marx and Weber. So, option 1 (1,2)—that's your answer.