Answer: to illustrate Claudius's skills of manipulation
Explanation: In this excerpt of Act IV, Scene VII, of "The Tragedy of Hamlet, Prince of Denmark", Shakespeare includes this plot event to illustrate Claudius's skills of manipulation. Claudius tells Laertes that Hamlet has been jealous of his use of the rapier, and then he nearly forces Laertes to duel with Hamlet and kill him with a poisoned sword instead of the bladeless rapier. To be sure of Hamlet's death he will add poison to a cup he will offer Hamlet if he outlives the duel.