Match control-system controller types to their characteristic operating advantages: (A) Pneumatic controller, (B) Hydraulic controller, (C) Electronic controller — pick the best mapping for explosion-proof operation, high-torque/high-speed actuation, and flexible/versatile operation.

Introduction / Context:
Industrial control systems use different controller technologies depending on safety, power, and versatility requirements. Knowing when to apply pneumatic, hydraulic, or electronic controllers is essential for plant design, robotics, and process automation.

Given Data / Assumptions:

• Pneumatic controllers use compressed air—no electrical sparks—making them suitable for hazardous environments.
• Hydraulic controllers use incompressible fluids and can deliver very high force and rapid response.
• Electronic controllers (analog/digital) offer programmability, compactness, and easy integration with sensors/PLCs.

Concept / Approach:
Match each technology to its hallmark advantage: safety in explosive atmospheres (pneumatic), power density and speed (hydraulic), and flexibility/programmability (electronic).

Step-by-Step Solution:

Verification / Alternative check:
Standards in process industries (e.g., refineries) commonly mandate pneumatic actuators/controllers in Zone 1/2 hazardous areas, while heavy machinery and robotics often employ hydraulics for force, and general automation uses electronic PID/PLC-based control for adaptability.

Why Other Options Are Wrong:

• A-1, B-3, C-2 or A-1, B-2, C-3: Assigns flexibility to pneumatic or explosion-proof to electronic—both contrary to practice.
• A-3, B-1, C-2: Claims hydraulics are chiefly flexible while electronics provide high torque—reversed.

Common Pitfalls:

• Assuming electronics are always permissible in explosive atmospheres without proper intrinsically safe barriers.
• Underestimating maintenance/cleanliness requirements for hydraulic systems.

Final Answer:
A-3, B-2, C-1