adventitious,uncertain,inconstant

So if the teacher wants to give a successful class, he should try his best to make the class colorful through controlling the tempo, such as the changeable speed, the density of the information, pace, etc.

因此,如果一位教师想把一节课上成功,他应尽力通过控制节奏使课堂丰富多彩,如以不定的速度,以教学内容的次重及不定的教学进度来进行教学。