Which of the following is an incorrect usage of 'complain'?

The choice that demonstrates incorrect usage of 'complain' is the phrase about complaining "with their friends." While it is possible for people to express their grievances to friends, the verb "complain" is most appropriately followed by either "of" or "about" when discussing what the complaint is concerning.

In the correct examples, "complained of" and "complained about" specify the subject of the complaint clearly. "Complain of" typically refers to a specific issue or discomfort, while "complain about" often pertains to a broader dissatisfaction, such as the quality of service. These prepositions are essential in clarifying the nature of the complaint. So, using "complained with" does not conform to the standard uses of the verb and creates confusion regarding the intended meaning.