Since the Sadducees do not believe in the resurrection, their question is obviously insincere. Their question is not really about an impossible marriage situation. They have a hidden agenda to challenge Jesus about the resurrection.
Jesus answer to them is a classical rabbinical answer. He uses Moses (whom they quoted) as the authority for his position in the place where Moses calls the Lord the God of
Abraham, the God of Isaac and the God of Jacob. He is the God not of the dead, but of the living. What more proof could you expect!!!
Jesus is the first Rabbi to use this unanswerable rabbinical answer – the authority from
Scripture. Most of the early Christians came from the Pharisees because they could more easily believe in the Resurrection of Jesus. Jesus consistently teaches both parties His message of Love.