How many half lives has an isotope gone theough if it has 12.5% of the radioactive substance remaining

Plants that have reproductive structures called cones are?

The theories on the expansion of galaxies maybe re-examined to strengthen science should not be tested to strengthen science will weaken scientific knowledge if they change will become laws if they don't change

Consider the following reaction: 2h2 + o2 —> 2h2o a) what are the reactants in this reaction? b) what are the products in this reaction? c) how many molecules of oxygen are used in this reaction?