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Compounds from different organisms are being used widely bu humans for their benefits. Some of the compounds are used as drugs. For example, penicillin is used as a drug or antibiotic. There are many plants which provides humans with other types of medicines and herbal remedies. There are other compounds which are used for cancer treatment. For example, taxol is a compound obtained from trees which are being used as anticancer drugs.
I think the correct answer is the second option. The best isotope to be used in dating metamorphic rocks would be potassium-40. It is the most common and is widely appliclable since most of metamorphic rocks have potassium in it. The isotope system used is potassium-argon.
