What elements’ isotopes are used to estimate how old something is? Why do scientists use more than one type?

An observation that requires measurement is called quantitative observable or qualitative

Which substance is a steroid? cholesterol fatty acid monosaccharide trans fat

The msds for glacial acetic acid says that it is a flammable liquid that can severely burn any human tissue it comes in contact with. it reacts with bases, various metals, and strong oxidizing agents. its vapors can form explosive mixtures with air.