Arrange the metric units in ascending order of length: 1. Centimeter, 2. Kilometer, 3. Decimeter, 4. Meter.

Introduction / Context:
This question tests familiarity with metric length units and their magnitudes. You must order them from smallest to largest value.

Given Data / Assumptions:

• Units: centimeter (cm), decimeter (dm), meter (m), kilometer (km).
• Ascending order required.

Concept / Approach:
Use base-10 conversions: 10 cm = 1 dm; 10 dm = 1 m; 1000 m = 1 km. Therefore, cm < dm < m < km.

Step-by-Step Solution:

Verification / Alternative check:
Convert a common base (e.g., 1 km = 100000 cm) to verify global ordering.

Why Other Options Are Wrong:
They contradict base-10 scaling (placing km before m, etc.).

Common Pitfalls:
Confusing decimeter with decameter; misremembering 1000 m in a kilometer.

Final Answer:
1, 3, 4, 2