Answer:
A: Radio waves.
Explanation:
Computers use short-wave radio in order to communicate with devices in it's immediate vicinity.
Multicast
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Answer:
Nancy's private key
Explanation:
She's receiving it. That means Matthew used her public key to encrypt it. She should decrypt it using her private key. Watch this video for clarification :)
Watch The Internet: Encryption & Public Keys on the big video site which cannot be named on brainly :p
The answer is C.54.45.43.54