A 7-year-old child understands that a tall, thin glass holds the same amount of liquid as a short, wide glass, even though they look different. According to Piaget's theory of cognitive development, this child has likely achieved which of the following?
✓ Correct Answer: Option B
Conservation is the understanding that quantity remains the same despite changes in appearance, a key milestone achieved during Piaget's concrete operational stage, typically by age 7.