500
A: I lost my keys last night. I ______________ (might/have/leave) them at your house. B: No, you _________ (could/have). You drove home with them. A: That's right. Then I _______________ (must/have/drop) them after I parked the car. B: You ____________ (might/have/lock) them in your car. Have you checked?
A: I lost my keys last night. I MIGHT HAVE LEFT them at your house. B: No, you COULDN'T HAVE. You drove home with them. A: That's right. Then I MUST HAVE DROPPED them after I parked the car. B: You MIGHT HAVE LOCKED them in your car. Have you checked?