观察下列等式

$\frac{1}{1\times 2}$ =1﹣ $\frac{1}{2}$ ， $\frac{1}{2\times 3}$ = $\frac{1}{2}$ ﹣ $\frac{1}{3}$ ， $\frac{1}{3\times 4}$ = $\frac{1}{3}$ ﹣ $\frac{1}{4}$ ，

下图是北半球某段河流河道形态和断面图，虚线表示河流主航道中心线。

【小题1】据图中信息，判断河流A---B河段的主要流向

读美国本土小意图及甲、乙两城市气候资料图，回答下列各题。

根据拼音写出相应的词语。

阅读下列短文，从每小题的三个选项中选出最佳选项。B
    Water comes from the sea, the rain and the tap. Animals, plants and human beings all need water. It is important for our daily (日常的）life. We use water to wash clothes and vegetables. We use water to cook food, make drinks, wash our face and so on. Firemen use water to put out fires. Fanners use water to grow crops. Water is useful. We mustn't waste (浪费）water. We must save water. Turn off the tap when you are brushing your teeth. Don't take a shower too long. Use the same water many times.