Psychologist research has found that students' attention generally changes with the teacher's lecture time. At the beginning of the lecture, the student's attention gradually increases, and the student's attention is maintained in an ideal state for a period of time. Began to spread. Which of the following, if true, would most weaken the conclusion? ['Teachers can get enough attention through proper arrangements.', 'Individual students can always stay focused throughout the process.', 'Interest is a key factor affecting concentration.', 'People can fully concentrate for only seven seconds.']