I'm not totally sure about Ms Help's answer although those expressions might convey the English meaning as well. Anyway, "Admit it!" is usually used like this: - You stole my wallet! - I did not! - Yes, you did! Admit it! So it's like: Admit that you've done something. - Who broke the television? - ... - Come on! Admit it! I know it was you! So, as for Ms Help's answers I think "认了吧" is best. Maybe you can also say "承认了吧" but I'm not sure. My Chinese isn't good enough, but I'm sure you know if it's correct. :P

Although Harregarre and I got off to a rough start he is quite right. Admit it primarily refers to a question of getting someone to express something they have yet to tell or say. You might have to be very sneaky to get someone to admit to something. If you have gotten to the point of saying to someone "admit it" your conversation has already gotten so confrontational, that it is unlikely anyone wants to admit anything. Thanx for the question

应该是"接受这个事实"或者"认了吧"的意思吧.