**Core Concept**
The concrete operational stage is a theoretical concept in developmental psychology, describing a stage of cognitive development where children develop the ability to think logically and solve problems using concrete objects and events. This stage is characterized by the development of operational thinking, which involves the ability to conserve quantities, understand causality, and think in terms of classes and categories.

**Why the Correct Answer is Right**
The concrete operational stage is typically observed in children between the ages of 7 to 11 years. During this stage, children develop the ability to think logically and solve problems using concrete objects and events. They begin to understand concepts such as conservation of liquid, weight, and volume, and can think in terms of classes and categories. This stage is a critical period of cognitive development, laying the foundation for the development of more abstract thinking in later stages.

**Why Each Wrong Option is Incorrect**
**Option A:** This age range is too young for the concrete operational stage, as children at this age are still in the pre-operational stage.
**Option B:** This age range is too old for the concrete operational stage, as children at this age are entering the formal operational stage.
**Option C:** This age range is incorrect, as the concrete operational stage typically ends before the age of 12.

**Clinical Pearl / High-Yield Fact**
The concrete operational stage is a critical period of cognitive development, laying the foundation for the development of more abstract thinking in later stages. It's essential to remember that children at this stage develop the ability to think logically and solve problems using concrete objects and events, which is a crucial milestone in their cognitive development.

**Correct Answer: C. 11 years.**