What Would You Infer from the Following Graph of the Number

Multiple Choice

What would you infer from the following graph of the number of temper tantrums in an AB design?
$$\begin{array} { l l l l l l l l l l } \text { Baseline: } 15 & 15 & 14 & 14 & 13 & 13 & 12 & 12 & 11 & 11 \\\text { Intervention: } & 10 & 10 & 9 & 9 & 8 & 8 & 7 & 7 & 6\end{array}$$

A) The intervention appears to be effective.
B) Maturation appears to be the most plausible explanation.
C) History appears to be the most plausible explanation.
D) Regression toward the mean appears to be the most plausible explanation.