What is the difference between convex and concave optimization objectives?

What is the difference between convex and concave optimization objectives?

• A. Convex: any local maximum is global; concave: any local minimum is global.
• B. Convex: any local minimum is global; concave: any local maximum is global.
• C. They always have the same global optimum.
• D. Convex functions have no local optima.

Answer: (D)