Which of the Following Best Illustrates the Concept of "Reaction

Which of the following best illustrates the concept of "reaction range?"

A) A child exposed to German in early childhood learns the language more quickly than a child exposed during adolescence.
B) A child who is not exposed to any language during infancy has problems speaking in early childhood
C) A young child with learning disabilities attends a low-quality public school in a poor neighborhood; his academic skills continue to deteriorate.
D) An adolescent who initially experiments with cigarettes and alcohol gradually uses these substances more frequently and in greater amounts over time.