The correct answer is (D) Creed; system or formula of beliefs. Also, a summary of Christian principles; a Christian liturgical creed, especially the Apostle's Creed or the Nicene Creed.

Credo comes from the first word ("I believe") in Latin of the Apostles' and Nicene creeds.

Examples of use:

• His credo appears to be let others do the work, but be sure to take the credit
• Her credo is to work hard, be kind to all, and hope that things will work out.