The policy having been made,the next problem was how to carry it out.

题目

The policy having been made,the next problem was how to carry it out.
为什么用having,不用had?

答案

注意两个短语之间用的是逗号,就是说,后面那段是主句,前面这句只是起修饰作用,按照一个句子里只能有一个（或两个并列的）谓语.