What elements’ isotopes are used to estimate how old something is? why do scientists use more than one type? (be specific, it is not just to get repeated results)

27. =3,500,000 x 4,000 = 14,000,000,000

The answer to the question: choose the correct statement.  a) when ethane reacts with fluorine gas the product is less stable.b) addition reactions of unsaturated hydrocarbons and halogens requires a high activation energy.  c)the double covalent bond within unsaturated hydrocarbons requires a lot of energy to break.  d)the double covalent bond within unsaturated hydrocarbons can be broken easily.is: a) when ethane reacts with fluorine gas the product is less stable.

At a given pressure, gas particles with smaller masses move faster.

Isnt it d im sure tell me if its wrong