Sunny(x)= x is a sunny day
Hot(x)=x is a hot day
All Sunny Days are hot:-
∀x (Sunny(x)->Hot(x))
Not All Sunny days are hot=Not(All sunny days are hot)
Not(∀x (Sunny(x) -> Hot(x)))
Not(∀x (~Sunny(x) V Hot(x) ) )
(∃ x ~(~Sunny(x) V Hot(x) ) )
∃ X(Sunny(x) AND ~Hot(x))
So, option D is the answer