What is the general form of the IF-THEN statement?

The general form of the IF-THEN statement in SAS is indeed that it checks a condition or expression and performs an action based on the evaluation of that condition or expression. The correct form among the options listed is framed as "IF expression THEN statement," which captures the essence of how the IF-THEN statement operates in SAS.

In this context, an "expression" represents a logical test that evaluates to true or false. When this expression is true, the specified statement or action that follows the THEN keyword is executed. This is fundamental to flow control in programming, allowing for conditional execution of code based on the evaluation of specific criteria.

Other phrases provided do not accurately reflect the syntax used in SAS. For example, "IF condition THEN action" is too vague and not a recognized syntax in SAS programming. Similarly, "IF condition THEN EXECUTE" and "IF expression THEN CALL" do not correspond to the typical structure of the statement as used in SAS code. The emphasis is on the idea that you are executing a specific statement when the condition or expression evaluates positively. Thus, the option correctly defining the general form is centered around using an expression that leads to a follow-up statement being executed.