To determine the absolute date of a sample of rock that is approximately 200,000 years old, the most suitable dating method from the options provided would be:
B) Potassium/argon dating.
Potassium/argon dating is effective for dating volcanic rocks and minerals that are older than about 100,000 years. In contrast, carbon/nitrogen dating (typically carbon-14 dating) is only useful for dating materials that are up to about 50,000 years old, making it unsuitable for your sample. Uranium/lead dating is also used for much older geological processes, typically millions of years old. Therefore, potassium/argon dating is the best method to use for a sample that is around 200,000 years old.