The correct option is µ.
Explanation
The International System of Units (SI) utilizes standard prefixes to denote decimal multiples and submultiples of base units. These prefixes simplify the notation of very large or very small physical quantities.
Analysis of Options:
- µ is Correct: The symbol µ (the Greek letter mu) stands for the prefix micro, which corresponds to a factor of 10-6 (one millionth).
- m is Incorrect: The symbol m stands for the prefix milli, which corresponds to a factor of 10-3.
- n is Incorrect: The symbol n stands for the prefix nano, which corresponds to a factor of 10-9.
- p is Incorrect: The symbol p stands for the prefix pico, which corresponds to a factor of 10-12.
Key Takeaway:
The SI prefix for the factor 10-6 is micro, represented by the symbol µ.