题目

--- Can you _________ all the money that I should pay?     --- Very sorry. Please wait a minute, madam.    A. add          B. add to       C. add up            D. add up to   答案：C用不等式表示：（1）x的3倍与7的和大于x与9的差： ；（2）x的一半与2的差是负数： ；（3）34x与2的和不小于x： ．