Answer:
da and pointing.
Explanation:
Skinner is the famous American psychologists and explains the human action that are dependent on the consequences of the previous actions. Depending on the consequences, the action was repeated.
Joseph has difficulty in ba and da. His teacher told him the difference by pointing and waving. Joseph learn to associate the da and ba difference. The da will be remembered more by him depending on the consequences. He also learn the pointing of the da.
Thus, the answer is da and pointing.
