In the interest of one's own reputation one should avoid ostentation while entertaining friends.

Answer: Option C

Ostentation : the pretentious or showy display of wealth and luxury, designed to impress.
Innocence : the state, quality, or fact of being innocent of a crime or offence.
Purity : freedom from adulteration or contamination.
Simplicity : the quality or condition of being easy to understand or do.
Miserliness : excessive desire to save money; extreme meanness.

Antonym of Ostentation is Simplicity