Final answer:
A picosecond is 1/1,000,000,000,000 of a second and is abbreviated as ps. It's used in physics to measure extremely short time intervals.
Step-by-step explanation:
The unit picosecond is 1/1,000,000,000,000 of a second. Therefore, the correct answer is d. Picosecond. The abbreviation for picosecond is ps, and it represents a trillionth of a second, which can also be written as 10-12 seconds. This measurement is especially used in physics and technology to describe events with very short time intervals, such as laser pulses and molecular dynamics.