Okay. So this one asks us which statements below correctly identify milestones in the concrete operational stage. We will just go through them and check them off if they are correct. So the first one is "Children are able to think logically about abstract concepts," and that is not something that we would expect in the concrete operational stage. That would be formal operational skills.

We're going to cross that one off. Number 2 is "Children are able to think logically about tangible or concrete concepts," and that is absolutely a milestone that we would expect to see in that stage. And then 3 is "Children master the principle of reversibility," and that is also something that we see in the concrete operational stage. Once they've mastered mental reversal, that also helps them to master the skill of conservation, right? So, based on this, our correct answers are 2 and 3. Both of those describe our concrete operational stage very nicely.

And there you go.