Let p,q,r be three mathematical statements. The statement (~p→q)→r is equivalent to
(~p∧q)∧(q∨r)
(~p∨r)∧(~q∨r)
(~p∨r)∨(q∨r)
a tautology
Consider (~p→q)→r we know that p→q = ~p∨q =~~p∨q →r=p∨q→r =∼(p∨q)∨r =(~p∧~q)∨r=(~p∨r)∧(~q∨r)
Therefore, the correct answer is (2).