Step 1: Understand the sequence of a feedback control loop.
In a feedback control system:
- Error detection (B) measures the deviation from the desired state.
- The controller (C) processes the error and adjusts the actuator.
- The actuator (A) applies the necessary adjustment to the system.
- The feedback sensor (D) detects the system’s new state and feeds it back to the controller.
Step 2: Conclusion
The correct order is: (B), (C), (A), (D).
Final Answer:
\[
\boxed{(B), (C), (A), (D)}
\]