take up on for learners of EnglishPowered by COBUILD
1. phrasal verb
If you take someone up on their offer or invitation, you accept it. [V n PP n] ⇒ Since she'd offered to babysit, I took her up on it.
2. phrasal verb
If you take a person up on something, you ask them to explain something that they have just said or done, for example because you think it is wrong or strange. [V n PP n] ⇒ She was making herself unnaturally casual. But he did not take her up on it.