An isotope used for absolute dating has a half-life of 100,000 years. Laboratory analysis of a crystal, which originally formed with only the parent isotope present, is now found to have a parent-to-daughter ratio of 1 :3. How long has it been since the crystal formed? * A. 33,000 years
B. 50,000 years
C. 200,000 years
D. 300,000 years