Monitor , printer , speaker , projector , keyboard etc
Assuming the data was encrypted with YOUR public key, you'll need YOUR private key to decrypt it. That's answer e.
a and b are not solutions by themselves, of course you need to use the decryption algorithm, but a key goes with it.
c would be about symmetric encryption, but this is asymmetric, so different keys are used for encryption and decryption
d is possible, but it would mean anyone can decrypt it (after all the key is public), so then there's no point in encrypting it in the first place.
So e is the only logical answer.
22 bits
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The designer could use the measurements in pixels.
