Correct metric units in quantity estimation for buildings Select the correct metric unit for the specified quantity when estimating for building works.

Introduction / Context:
Unit consistency underpins correct quantity takeoff and BOQ preparation. Misstating units causes serious errors in costing, ordering, and measurement. Estimation relies on SI-based metric units for all basic and derived quantities on site.

Given Data / Assumptions:

• Standard SI/metric practice in civil estimation.
• Length, area, volume, mass/weight, and capacity must use correct units.
• One best answer is expected.

Concept / Approach:
In SI: length → metre (m); area → square metre (m^2); volume → cubic metre (m^3); capacity (fluids) → litre; mass → kilogram (kg) whereas weight (force) → newton (N). Among the options, only one is unambiguously and universally correct without contextual caveats.

Step-by-Step Solution:

Verification / Alternative check:
Cross-check BOQs: plastering measured in m^2, concrete in m^3, rebar mass in kg (mass) but load in N/kN. Only (a) fits without nuance.

Why Other Options Are Wrong:

• Cubic metre for area: wrong dimension.
• Square metres for volume: wrong dimension.
• Kilogram for weight: weight is force; SI unit is newton.
• Litre for capacity: commonly used, but the question expects the single most canonical mapping; hence (a).

Common Pitfalls:
Confusing mass with weight; interchanging area and volume units; ignoring that capacity (litre) is derived and context-dependent.

Final Answer:
Metre for length