Which of the following networks major networks contain an incorrect subnet mask?

Class C with a mask 255.255.255.0 or /24

Class A with a mask 255.0.0.0 or /8

Class B with a mask 255.255.0.0 or /16

Class D with a mask 255.255.255.255 or /32

Answer:
Class D with a mask 255.255.255.255 or /32

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