Create a flowchart that outlines when to use dimensional analysis and when to use scientic notation

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).

It will be b hydrogen

The answer is  d.  hydrogen