Listen again and complete the conversation. Mechanic 1: It looks like the engine completes 1 _______________, though. Mechanic 2: Right. Then it 2 _______________ the compression stroke. But then it stops. Mechanic 1: Do you think the spark plug is 3 _______________ the gas? Mechanic 2: I thought of that. I tested a new one and the same thing happened. I have another idea, though. Mechanic 1: What's that? Mechanic 2: I think it's leaking fuel in 4 _______________ Mechanic 1: So there isn't 5 _______________ or fuel to set off the explosion? Mechanic 2: Precisely. That could also prevent 6 _______________from occurring.