Final answer:
The quote 'What splendid king you'd make of a desert island-- you and you alone in this line' is from the play 'The Tempest' by Shakespeare and is said by Prospero to his daughter Miranda. Prospero is referring to the idea of ruling the island by himself.
Step-by-step explanation:
The quote 'What splendid king you'd make of a desert island-- you and you alone in this line' is from the play 'The Tempest' by William Shakespeare. It is said by Prospero, the protagonist, to his daughter Miranda. Prospero is a powerful sorcerer and has the ability to control the spirits on the island. He mentions this line in reference to the idea that he would be able to rule over the island if he were the only person there. He says this to Miranda to reflect on their current situation and to hint at his plans for their future on the island.