What Is the Difference Between a Negawatt and a Megawatt

What is the difference between a negawatt and a megawatt?

A) A negawatt is a megawatt of energy saved,while a megawatt is a million watts of energy used.
B) A negawatt is any amount of energy saved,while a megawatt is a measure equal to a million watts of energy.
C) A negawatt is the equivalent of 1 kilowatt of energy saved,while a megawatt is the equivalent of 1 kilowatt of energy used.
D) A negawatt is one thousand watts,while a megawatt is one million watts.