The answer is a. dwwdfn dw gdzq
When you shift the letters advancing (offset) to 3 characters, your new alphabet chart would be :
Plain Alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ
Caesar Alphabet (+3) DEFGHIJKLMNOPQRSTUVWXYZABC
D would be the start of the Caesar alphabet as you advanced to 3 characters: A B C. Then look at the new equivalent letters from Plain alphabet row to Caesar alphabet row.
A T T A C K A T D A W N
D W W D F N D W G D Z Q
