Explanation:

- Let's arrange the units of measurement from smallest to largest:

- Micron (1): One-millionth of a meter

- Millimetre (4): One-thousandth of a meter

- Centimetre (6): One-hundredth of a meter

- Metre (2): The basic unit of length

- Kilometre (5): One thousand meters

- Mile (3): Approximately 1,609 meters

- Analyzing the options:

- Option 1: 1-4-6-2-3-5

- Incorrect sequence, as a mile is longer than a kilometer.

- Option 2: 1-4-6-2-5-3

- Correct sequence, from smallest to largest.

- Option 3: 4-6-2-5-1-3

- Micron is not accounted for before millimetre.

- Option 4: 4-6-2-5-3-1

- Incorrect, Micron should come before millimetre.