Answer:
Polonius's idea for uncovering the truth about Hamlet apparent madness is to A. Spy on him
Step-by-step explanation:
Although Hamlet is a tragedy, Polonious (the father of Olivia) is one of the main sources of comic relief. He tells the King and the Queen that the reason why Hamlet is acting weird is because he is in love with his daughter (besides, Polonious is a very self-centered character, in case you haven't noticed!). Therefore, he plans along with the king and queen to spy on Hamlet.
Bear in mind that there are several instances of Polonious spying on Hamlet, once he listens to an interaction that Hamlet has with his daughter, Ophelia. Another instance takes place when Hamlet is talking with his mother. The latter ends up in the death of Polonious, he was hiding behind a curtain and Hamlet thinks that he is the king or an intruder and stabs him through the curtain.