What does the word incredulous mean? in the short story "through the tunnel"?

Read the following excerpt from anne frank remembered by miep gies. i said to myself, you can do what you like, even drink poison, but i will stay here. then he said again, "i'll be back to check on you. one wrong move and off you go to prison too." he turned and shut me into the room alone. i had no idea where he'd gone. i had no idea what was going on in the rest of the house. i was in a terrible mental state. i felt as though i were falling into a bottomless hole. which sentence from the excerpt would a prepared speaker best use to support the viewpoint that miep gies was in terrible danger? i said to myself, you can do what you like, even drink poison, but i will stay here. then he said again, "i'll be back to check on you. one wrong move and off you go to prison too." i had no idea what was going on in the rest of the house. i felt as though i were falling into a bottomless hole.