Question

Which of the following is not equivalent to p → q.

Options

• p only if q

• q is necessary for p

• q only if p

• p is sufficient for q

Answer 1

q only if p

Explanation:

p → q means, 

(i) pis sufficient for q

(ii) p only if q

(iii) q is necessary condition for p

(iv) ~ q → ~ p.