What statement should be inserted to calculate the quarterly total from the monthly sales data?

The choice that calculates the quarterly total from the monthly sales data effectively utilizes the SUM function in SAS. By specifying SUM(of month{*}), the statement systematically adds together all monthly sales data contained within the variable "month." The asterisk serves as a wildcard that indicates all elements of the array "month," ensuring that all associated monthly values are included in the summation, regardless of how many months are present.

This approach is robust because it automatically accommodates changes in the number of months represented in the data. If more months were added later, the same statement would still correctly reference all values without needing any modification. This flexibility is particularly essential for maintaining accurate calculations in scenarios where data structure might change.

The other choices are less effective in calculating the total for a quarter. One option explicitly lists only the first three months without the use of the SUM function, meaning it wouldn't automatically adjust for any changes to the dataset or additional months. Another choice includes only the first two months, which would not represent a complete quarterly total. Lastly, one alternative uses an improper syntax for the SUM function, which would lead to errors in execution. Thus, the chosen statement is not only correct but is also the most efficient method for summing multiple values in SAS programming