Complete the conversations use can or can't and the words in the box

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Person A: I __ find my keys anywhere.
Person B: Don't worry, I'm sure you can find them if you look carefully.

Person A: I __ believe how quickly time is flying by.
Person B: I know, it's crazy how fast things are changing.

Person A: I __ believe you made it to the concert on time.
Person B: Yeah, I left really early so I could beat the traffic.