A combined arms system cannot work without effective _________.Select one:a. Surveillance.b. Command and control.c. Propaganda.d. Reconnaissance.

To determine the correct answer for the role that is essential for a combined arms system to function effectively, let's analyze each of the options provided:

1. Surveillance: This involves monitoring enemy movements and activities, which is important but not solely sufficient for the entire system's effectiveness.

2. Command and control: This refers to the exercise of authority and direction by a commanding officer over assigned forces. It is critical for coordinating various branches of armed forces, making it a strong candidate.

3. Propaganda: While important for influencing public opinion and morale, it does not directly impact the operational capability of a combined arms system.

4. Reconnaissance: This refers to military observation of a region to locate an enemy or ascertain strategic features. It is crucial for gathering information.

Analysis:

• While surveillance and reconnaissance are important for understanding enemy positioning, they do not ensure coordination of actions.
• Command and control (b) is essential because, without proper command structure and communication protocols, even the best-laid plans can fail due to lack of coordination among the different branches of the military.

Conclusion:

Given the requirements for a combined arms system to be effective, the best answer is b. Command and control.