Relation between the ratio of specific heat and degree of freedom is given by,
γ=1+f2...(1)
For monoatomic molecule, A, f=3
⇒γ=1+32=35
For diatomic rigid molecule B, f=5
⇒γ=1+52=57
For diatomic non-rigid molecule C, f=7 ⇒γ=1+72=79
For Triatomic rigid molecule D, f=6 ⇒γ=1+62=34