Choose the correct answer. The headmaster saw some boys ... in the corridor and told them to stop ... .

After a verb of perception, “see somebody + -ing” describes an action in progress (“saw some boys fighting”); “see” is never followed by “to + infinitive” in the active voice. “Stop + -ing” means to end an activity (“stop fighting”), whereas “stop to fight” would mean to stop in order to start fighting. So both gaps take “fighting”.

Manba: UZBMB namunaviy test topshiriqlari (2022, mutaxassislik)