Question

a fossil of a marine crab, suspected to be 500 million years old, is discovered in south america. which of the following is the most accurate way of determining the age of the fossil?
dating the strata the fossil was found in
radiometric dating of igneous rocks near the fossil using 40k
comparing the fossil to other fossil organisms in the same strata
use of a molecular clock
14c dating of the fossil

Explanation:

Radiometric dating of igneous rocks near the fossil using 40K is a reliable method for dating very old fossils. Dating strata gives a general age - range, comparing fossils in strata is relative dating, molecular clocks are for recent evolutionary time - scales, and 14C dating is only useful for up to about 50,000 years old samples.

Answer:

Radiometric dating of igneous rocks near the fossil using 40K