Answer:
a. Children begin to use language.
Explanation:
Concrete-operational stage: In psychology, the concrete-operational stage is one of the stages of the Piaget's cognitive developmental theory, and is considered to be as the third stage. The stage begins at the age of seven years and lasts through the age of eleven years. This stage is distinguished by the development of logical thoughts.
Characteristics or elements:
1. Conservation.
2. Classification.
3. Seriation.
