Arrange the metric length units in strictly ascending order of magnitude (smallest to largest): 1) Centimetre (cm), 2) Kilometre (km), 3) Decimetre (dm), 4) Metre (m).

Introduction / Context:
Metric unit sequencing is a common reasoning task. Understanding base-10 relationships between centimetre (10^-2 m), decimetre (10^-1 m), metre (10^0 m), and kilometre (10^3 m) makes ascending or descending orders straightforward once you translate each unit to its power of ten relative to metres.

Given Data / Assumptions:

• Units: centimetre (1), decimetre (3), metre (4), kilometre (2).
• We need ascending (smallest → largest).

Concept / Approach:
Express each unit as a power of metre: cm = 10^-2 m, dm = 10^-1 m, m = 10^0 m, km = 10^3 m. Ordering powers from lowest to highest yields cm → dm → m → km.

Step-by-Step Solution:
Centimetre (1) is the smallest.Then Decimetre (3).Then Metre (4).Largest: Kilometre (2).Therefore: 1, 3, 4, 2.

Verification / Alternative check:
Convert a sample: 1 km = 1000 m, 1 m = 10 dm = 100 cm. This confirms strict inequalities: cm < dm < m < km.

Why Other Options Are Wrong:

• Any option placing km before m or dm violates magnitudes.
• Swapping cm and dm misreads decimal positions.

Common Pitfalls:
Mixing up deci- (10^-1) and centi- (10^-2); remember “centi-” is smaller than “deci-.”

Final Answer:
1, 3, 4, 2