A substrate is a reactant that is catalyzed by an enzyme.
That would be B - Metabolism.
Mutations can be any but id say all besides always harmful or all of the above if that’s a choice
In a water molecule (H2O), the oxygen nucleus with +8 charges attracts electrons better than the hydrogen nucleus with its +1 charge. ... The hydrogen atoms are not only covalently attached to their oxygen atoms but also attracted towards other nearby oxygen atoms. This attraction is the basis of the 'hydrogen' bonds.