题目

Every time ______ they met , they would talk several hours together about the persons and things _______ they remembered in the middle school. A. that; who and which       B. when ; which       C. /; that       D. which ; /  答案：C下列命题中是全称命题的是…(    )A.圆有内接四边形B.存在x,使x2-4=0C.有一个数列,既是等差数列,又是等比数列D.存在一个函数,既是偶函数,又是奇函数