Identify the fundamental (base) mechanical units used in the S.I. system for length, mass, and time.

Introduction / Context:
The S.I. system is built on seven base quantities; in mechanics, the core trio is length, mass, and time. Knowing their correct base units avoids confusion when checking dimensions, doing unit conversions, or comparing legacy literature (C.G.S., F.P.S.) to S.I.

Given Data / Assumptions:

• We focus on mechanical bases only (L, M, T).
• Options mix metric and imperial magnitudes and different time scales.
• The correct S.I. base magnitudes are metre, kilogram, and second.

Concept / Approach:

Dimensional consistency relies on the base set. Any deviation (e.g., using centimetre or minute) leads to scaled systems (C.G.S.) or mixed units (non-S.I.).

Step-by-Step Solution:

Verification / Alternative check:

Check dimensional equations: force = mass * acceleration → N = kg * m/s^2, directly referencing the base trio.

Why Other Options Are Wrong:

• Centimetre, gram, second: C.G.S. scaling, not S.I.
• Foot, pound, second: Imperial system, not S.I.
• Kilometre, kilogram, minute: Mixed/derived magnitudes; not base units.
• None of these: Incorrect because a correct S.I. base set is present.

Common Pitfalls:

• Using minutes or hours in dynamics without converting to seconds, causing numerical errors.
• Confusing weight (force) with mass in base definitions.

Final Answer:

Metre, kilogram, second