Unit1：

　　1.What factors may weaken one's memory?

　　It is often reported that long-term poor nutrition may affect the functioning of the brain, thus damaging both the long-term and short-term memory. Also harmful to one's memory is lack of water. Elderly people need plenty of water to guarantee their memory works. A third factor is lack of sleep. Without enough sleep, one may feel tired and have difficulty concentrating, not to mention learning things by heart.