Final answer:
The metric prefix "pico" (symbol p) represents a factor of 10^-12 in the metric system, making Option 2 the correct answer.
Step-by-step explanation:
The metric prefix "pico" (symbol p) in the metric system means a factor of 10-12. It's used to denote very small measurements in scientific calculations. This means that Option 2, which states a factor of 10-12 (0.000000000001), is the correct answer. In context, when talking about the diameter of atoms, which can vary from 1 x 10-10 m to 5 x 10-10 m, the prefix pico is too small, and the prefix nano (n, representing 10-9) is too large, thus the measurement is often expressed in angstroms (Å), where 1 Å = 10-10 m.