Equivalent logical expression for the Well Formed Formula $(WFF)$,
$\sim(\forall x) F\left[x\right]$
is
~(∀x) F(x)
=(∃x)(~F(x))
So ans is C
Negation of all of 'x' is equal to there exist 'x', so C is the answer
When negation is brought before the atom, ∀ is converted to ∃ and vice versa.