The correct option is C innocent
The word 'guilty' refers to being responsible for a specified wrongdoing.
Option A, true refers to being in accordance with fact or reality
Option B, right refers to being morally good, justified or acceptable.
Option C, innocent refers to being not guilty of a crime or offence.
Option D, correct refers to being free from error.
Thus, according to the meaning, the word 'innocent' is the opposite of the word 'guilty'.