During which stage of Piaget's cognitive development do children become able to think abstractly?

The other options are incorrect because they do not match the criteria described in the question. Children in the sensorimotor stage are focused on developing motor skills and do not have the ability to think abstractly. Children in the preoperational stage are still in the process of developing cognitive skills and primarily think in a concrete and literal manner. The concrete operational stage is characterized by the ability to think logically and understand cause and effect relationships, but still lacks the ability to think abstractly. The formal operational stage is the only stage where individuals are able to think abstractly, apply hypothetical reasoning, and understand complex concepts beyond their direct experiences.