You must have forgotten to attach some options so that someone could give you the right answer. Anyway, it's common question in many tests, so I think I got what you mean. I am pretty sure you have thus option given "They say the lunatic's strength is superior but I managed to keep close behind him. When he speeded up, I ran even faster to try and catch up with him." This one clearly represents the irony tool, so do not hesitate to use it.