Final answer:
The statement if (isTested) is a valid control expression in some programming languages but not in others.
Step-by-step explanation:
In programming languages, a control expression is a condition that determines whether the code inside a certain block should be executed or not. In this case, the student is asking if the statement if (isTested) is a valid control expression in three different programming languages. The answer is that it depends on the language.
In languages like Python and JavaScript, the condition in an if statement needs to evaluate to either true or false. So in those languages, the correct control expression would be if (isTested == true) or if (isTested == false). However, in languages like Java, the statement if (isTested) is valid because Java treats any non-zero value as true and zero as false.
Therefore, the statement if (isTested) is a valid control expression in some languages, but not in others.