Industrial robots are built from three basic components: power supply, control (memory) console, and which third element that actually executes motion?

Introduction / Context:
A robot is a mechatronic system that senses, plans, and acts. Core subsystems include the energy source, the controller (logic, memory, servo loops), and the mechanical structure that converts control outputs into motion at the tool center point (TCP).

Given Data / Assumptions:

• Power supply feeds drives and electronics.
• Control console stores programs and closes loops with sensors.
• The remaining component must be the motion-executing mechanism.

Concept / Approach:
The mechanical unit (arm) comprises links, joints, gearboxes, actuators, and end-effectors. It is the physical interface that manipulates parts, tools, or sensors in space according to commands from the controller and feedback from encoders or torque sensors.

Step-by-Step Solution:
1) Enumerate robot fundamentals: power, control, mechanism.2) Match “mechanical unit (arm)” as the executor of motion.3) Exclude items that are accessories (cables), sub-components (microcomputer within controller), or peripherals (software alone, reservoirs).

Verification / Alternative check:
Any robot datasheet identifies axes, reach, payload (mechanical), alongside controller model and power specifications, confirming this triad.

Why Other Options Are Wrong:
Coaxial cable: wiring, not a major robot subsystem. Microcomputer: part of the controller. Software: necessary but not the mechanical executor. Hydraulic reservoir: component for certain actuators, not universal nor the third core subsystem.

Common Pitfalls:
Overemphasizing software while forgetting the physical mechanism that performs work.

Final Answer:
Mechanical unit (arm).