The correct option is C pious
The word 'wicked' refers to being evil or morally wrong.
Option A, innocent refers to being not guilty of a crime or offence.
Option B, decent refers to something of an acceptable standard.
Option C, pious refers to being devoutly religious.
Option D, peaceful refers to being free from disturbance.
Thus, according to the meaning, the word 'pious' is the opposite of the word 'wicked'.