Checking satisfiability of a boolean expression means it asks whether the variables of a given Boolean formula can be consistently replaced by the values TRUE or FALSE in such a way that the formula evaluates to TRUE.
It is the first problem to be proved NP complete.
now ,
so option a is true.
Now a boolean formula can either be in Conjunctive normal form or in Disjunctive normal form and we can convert from Conjunctive normal form to Disjunctive normal form .so both are equivalent when we try to check its satisfiability.
so all of the given problems is NP complete.
Correct option is None of these.