Admit to (doing) sth何时可以省略to?

问题描述:

Admit to (doing) sth何时可以省略to?
看牛津上说.admit to (doing) sth是固定短语.但是后面的例句又有省略了to的.
是可以省略介词to呢,还是在特定情况上才能省略?

当admit表示“承认”时,它的介词to 可以省略.
1 she admitted to having been there
2 she admitted having been there
3 she admitted (to the fact) that she had been there.