During Piaget's Third Stage of Cognitive Development, Called the Concrete

During Piaget's third stage of cognitive development, called the concrete operational stage (ages 6-11) , children ________.

A) gain the ability to systematically solve problems without resorting to trial and error
B) gain the ability to reason about abstract concepts and problems
C) develop the ability to realize that objects still exist when they are not being sensed
D) develop the ability to perform mental operations on real, or concrete, objects and events