## **Core Concept**
The question pertains to the developmental stages of the mind, particularly referencing Jean Piaget's theory of cognitive development. This theory outlines four stages: Sensorimotor, Preoperational, Concrete Operational, and Formal Operational.

## **Why the Correct Answer is Right**
The Concrete Operational stage, according to Piaget, occurs approximately between the ages of 7 to 11 years. This stage is characterized by the child's ability to think logically about concrete events and understand the concept of conservation. Since children typically start first grade around the age of 6 or 7, the development of the Concrete Operational stage aligns with this timeframe.

## **Why Each Wrong Option is Incorrect**
- **Option A:** The Sensorimotor stage (0-2 years) is too early for first grade age.
- **Option B:** The Preoperational stage (2-7 years) partially overlaps with the age children start first grade but is not the stage they are in at that point.
- **Option D:** The Formal Operational stage (11 years and up) is too late for the age children start first grade.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that children around the age of 7 start to develop logical thinking about concrete objects, marking the beginning of the Concrete Operational stage. This is crucial for educators and parents to understand, as it influences how children learn and interact with their environment.

## **Correct Answer:** C. Concrete Operational.