Which of the following conditions can be expressed by a Boolean formula in the Boolean variables p1,p2,p3,p4 and the connectives ∧ ∨, (without ¬ ) ?
I. At least three of p1,p2,p3,p4 are true.
II. Exactly three of p1,p2,p3,p4 are true.
III. An even number ofp1,p2,p3,p4are true.
(A) I only
(B) II only
(C) III only
(D) I and III