The correct answer is B.
The conductor said that if the person wanted to smoke, they would have to go out. This is a conditional statement, which means that the conductor is not ordering the person to go out and smoke, but is simply stating that this is what they would have to do if they wanted to smoke.
Option A is incorrect because the conductor is not ordering the person to go out and smoke. They are simply stating that this is what they would have to do if they wanted to smoke.
Option C is incorrect because the conductor is not telling the person that smoking is not permitted in the bus. They are simply stating that if the person wants to smoke, they would have to go out.
Option D is incorrect because the conductor is not telling the person that they will have to go out and smoke. They are simply stating that this is what they would have to do if they wanted to smoke.