下列说法正确的是 . (写出所有正确说法的序号) ① 若的必要不充分条件; ② 命题; ③ 设命题“若则”的否命题是真命题; ④ 若; 答案:①③;The little boy often makes his mother ______him ______. A. talk; something interesting B. tell; something interesting C. say; interesting something D. speak; interesting something