Answer: C. Irony
Irony is a rhetorical device in which an event appears to be, on the surface, radically different from what it actually is. It can be classified into verbal irony, dramatic irony and situational irony.
In this case, the author is using irony to describe the pleas of the son. He is asking his father to come back, and vehemently promising to take his place. He sounds absolutely determined to take his father's place. The irony comes when the father responds. As soon as he waves, the son falters, regrets the offer and leaves the father.