For a spontaneous reaction, ∆G∘= negative Using relation, ∆G∘=∆H−T∆S For ∆G to be negative either ∆S is + ve and ∆H is + ve at very high temperature or ∆S is + ve and ∆H is-ve at low temperature. So, for B and C the value of ∆G∘ comes out to be negative and hence reactions are spontaneous. So, options (c) is correct.