The half-life of a certain element is 100 days. how many half-lives will it be before only one eighth of this elementremains?

It is a mixture. simply put, a compound must be pure, that is, of only one chemical structure and composition. a mixture is made of different chemical substances (i.e. elements, molecules, compounds) that are not chemically bonded to each other, but instead physically grouped together, as in the case of gasoline (a homogeneous solution).

Um i think answer is a

It is a ok  i know i have a brain functioning well.