Final answer:
The best paraphrase of the bolded line is 'what reply should be given by the son of a king when someone asks him like a sponge.'
Step-by-step explanation:
The best paraphrase of the bolded line is 'what reply should be given by the son of a king when someone asks him like a sponge.' In this context, Hamlet is expressing his frustration at being questioned like a sponge – someone who absorbs information without giving anything in return. Hamlet is saying that he is capable of keeping someone's secret, but he wonders why he should be expected to do so when he is not trusted with his own secrets.