参考范文：
　　As students, we have to study almost every day. However, not everybody knows how to study efficiently.Do you want to know better about it?
　　There is some relationships between the study efficiency and the hours spent in studying in a day.In fact, more hours of study do not necessarily result in better or higher study efficiency.It is said that the optimum of efficiency comes when one studies about 5 hours and the efficiency begins to drop as he studies longer than it. By the time when one studies 11 hours per day， his efficiency of study becomes very poor.
　　In conclusion, there is always a maximum of efficiency and an appropriate amount of time for study in a day. More time spent in study doesn’t always mean greater efficiency.