The composition would be more "diluted" in a sense.
Hydrogen as it has only 1 proton and therefore only an atomic mass of 1...
My thought would be B) gases.
I could be wrong but that's what i'd say
Adding an atom will increase the repulsion between existing atoms and lone pairs. Added atom will result in bond pair-bond pair and bond pair-lone pair repulsion. The magnitude of the lone pair-bond pair repulsion is greater than the bond pair-bond pair repulsion. The added atom will change the electron geometry and bring about a distortion in the molecular geometry.