Answer:
He is suspenseful when the audience is playing god because it´s the film and audience that make their own guesses.
Explanation:
Hitchcock believes you have suspense when you let the audience play God. Meaning when there is uncertainty in what´s going to happen in a film and the audience makes their own guesses. The writer calls it playing god because the audience knows the fate of the characters and what may happen to them in the future.