The correct option is C dismissal
The word 'appointment' refers to an act of assigning a job or position to someone.
Option A, disappointment refers to sadness or displeasure caused by the non-fulfilment of one's hopes or expectations.
Option B, discharge refers to an official way of telling someone that they can or must leave a place or situation.
Option C, suspension refers to the act of adjournment.
Option D, dismissal refers to the act of removing someone from employment.
Thus, according to the meaning, the word 'dismissal' is the opposite of the word 'appointment'.