有道题看了好久，感觉题目意思都懂了，但是就是后面那个选项B是什么意思愣是不明白。。。求指点 T=｛2,3,5,6,7,8,9｝ A：the total number of positive 4-digit integers that can be formed where each digit is in set T and the 4 digits in each 4-digit integer are different from each other B:(7)(6)(5)(4) 比较大小。
