"the manager of a fruit-and-vegetable shop places in his window, among the onions and carrots, the slogan: "workers of the world, unite! why does he do it? what is he trying to communicate to the world? is he genuinely enthusiastic about the idea of unity among the workers of the world? is his enthusiasm so great that he feels an irrepressible impulse to acquaint the public with his ideals? has he really given more than a moments thought to how such a unification might occur and what it would mean?

Answer and Explanation:

The answer is explained in the very next paragraph.

The manager does that because "That poster was delivered to our greengrocer from the enterprise headquarters along with the onions and carrots" (Excerpt from the passage)

Basically what they want to convey is that, the people they never understand the meaning of most of the slogans. He did it because it had be done for years and everyone does it.

That's how things work. If he refuses, he could get into trouble.

all of them make sense but, i would have to say ask someone who has been there/or lives there, and/or read recent newspapers from that city.

hope this !