The correct answer is (C) To combine (two or more elements, ingredients, substances, words or phrases); to mix; to construct; to form a composite whole by combining parts or elements. To compute (interest) on the total of principal and previously accrued interest.

Compound comes from Middle Englsh compounen, Latin componere (put, place together).

Examples of use:

• He compounded a merchandising plan from the input of his three assistants. To compound a felony. to compound a new plan from parts of several former plans..
• His skills compound superb coordination, strength, and speed.