3. "What do you do?"
After you make a soft GM move, ask "What do you do?" This hands the conversation back to the player(s) and prompts them to say something.
You don't have to literally say, "What do you do?" Sometimes, your move will include a question. When portraying an NPC, you might make your move and just look at the players expectantly. But if you're unsure, ask: "What do you do?"
If they say something that doesn't make sense—something you think is impossible, invalid, or unreasonable—then tell them that. Clarify the fiction. If they persist, tell them the consequences and/or requirements. Ask if they still want to do it.
If they ask questions, answer them. If the answers aren't obvious, tell them the requirements. "You'll have to poke around a bit and Seek Insight." Then put the ball back in their court: "What do you do?"