Sleep effect refers to the phenomenon that the communication effect of information will change with the passage of time. That is, after a period of time, the positive effect brought by some information is decreasing, while the negative effect brought by some information is transformed into positive effect.
According to the above definition, which of the following phenomenas belongs to sleep effect?
Teacher repeatedly explained to the students how to calculate the area of a triangle, but the students still couldn't correctly calculate the area of a triangle