What is the output syntax for summing variables using a variable list in SAS?

The correct syntax for summing variables using a variable list in SAS is designed to efficiently specify a range of variables. In this case, using "of qtr1 - qtr4" is the proper way to reference a set of contiguous variables. This syntax not only succinctly signifies the variables from qtr1 through qtr4 but also clearly instructs SAS to treat them as a collective entity when performing the sum operation.

This approach leverages SAS's capability to handle variable ranges, which is particularly useful when there are many variables that follow a sequential naming pattern. The "of" keyword, combined with the dash to indicate a range, allows for cleaner and more manageable code.

In contrast, other choices involve either incorrect use of syntax or do not adhere to the concise conventions SAS offers for handling multiple variables. Specific references to individual variables or using the incorrect method of summation would produce errors or not yield the expected results. The choice that employs "of qtr1 - qtr4" aligns with SAS's syntax and best practices for summing a sequence of variables effectively.