Define open-loop and closed-loop control in the context of instrumentation labs.

• A. Open-loop uses feedback; closed-loop does not.
• B. Open-loop applies a control input that relies on process output.
• C. Open-loop applies a control input without feedback; closed-loop uses feedback from the process output to adjust input toward a setpoint.
• D. Both use feedback in the same way.

Answer: (C)