Sophia Finds That Her Son Alex Enjoys Lemon Candy

Sophia finds that her son Alex enjoys lemon candy. Sophia encourages Alex when he displays courteous behavior at home. She then starts reinforces this behavior at school, relatives' homes, and church. What type of single-case design does Sophia employ?

A) Across situations multiple-baseline design
B) Across behaviors ABA design
C) Across subjects multiple-baseline design
D) Across subjects ABA design