Internal speech: A kind of speech to yourself, a kind of silent speech accompanied by thinking about the problem. Which of the following is internal speech? ["The trainees whispered about the teacher's teaching method.", 'Looking at the forest outside the window, Lao Zhang is lost in thought.', 'Xiao Li stood up, looked at the teacher timidly and said, "I don\'t know".', 'Lao Li and Lao Zhao argued loudly about whether to fight.']