The \texttt{avg()} method is not directly available in pandas for DataFrame objects. Instead, you can use the \texttt{mean()} method to calculate the average of numerical columns. While \texttt{sum()}, \texttt{count()}, and \texttt{mean()} are commonly used Descriptive Statistical methods in pandas, \texttt{avg()} is not one of them. Therefore, the correct answer is \texttt{avg()}.