Final answer:
According to Piaget, someone who takes things very literally and cannot understand the difference between necessary and sufficient conditions is in the concrete operational stage of cognitive development.
Step-by-step explanation:
According to Piaget, someone who takes things very literally and cannot understand the difference between necessary and sufficient conditions would be in the concrete operational stage of cognitive development. This stage occurs from about 7 to 11 years old. In this stage, children can think logically about real events, but they have not yet developed the ability to understand abstract concepts or hypothetical situations where necessary and sufficient conditions come into play.