What is the Karel command to check if there are no beepers?

The command to check if there are no beepers is structured as a logical expression where the presence of beepers is negated. The correct option employs the logical NOT operator, which is represented by the exclamation mark (!).

Thus, the command !hasBeeper(); effectively checks if the condition of having a beeper is false. In programming, this means that when you call hasBeeper(), it returns true if Karel has at least one beeper. By negating this with the exclamation mark, you obtain true when Karel has no beepers, fulfilling the requirement of the question.

Other options may misrepresent the intended check. For example, not(hasBeeper()); may seem correct syntactically but is not the standard way Karel's commands are expressed in this context. Commands like hasNoBeepers(); and checkNoBeepers(); do not exist in Karel's command set, making them invalid choices. Therefore, the use of the logical NOT operator in conjunction with the hasBeeper() function is the correct approach.