由市文明办、团市委、市教育局组织的2016年“柳州好少年”评选结果揭晓，初一学生范娜榜上有名。范娜，今年13岁，2013年父亲在工地上不幸坠亡，母亲丢下她和3岁的弟弟另嫁他人，爷爷奶奶年老多病。她为了帮助爷爷奶奶撑起这个家，在勤奋学习之外，回到家还要照顾年幼的弟弟，帮爷爷奶奶干家务活，星期天去捡废品卖补贴家用。生活的压力没有压垮这位13岁的女孩，她不仅学习成绩优秀，还经常帮助办理有困难的学生。

出勤率（  ）

写出下列单词的—ing 形式

小明在老师的指导下用小球和弹性很好的轻质橡皮筋等器材进行了如下实验与探究：让一系于橡皮筋一端的小球从某悬挂点O的正下方P点由静止释放如图甲所示，整个下落过程中，橡皮筋所受弹力F与小球下落高度h的关系如图乙所示；小球下落的速度v与下落高度h的关系如图丙所示。已知该轻质橡皮筋每受到0.1N的拉力就伸长1cm，经测量小球从P点下落到A、B、C三点的距离分别为：h_a=0.4m，h_b=0.5m，h_c=0.7m。（不计空气阻力）.

阅读理解

    Nowadays people are putting our water supply in danger, because they use too much water or throw rubbish into the river. You may wonder how paving(铺砌) a road can lead to less usable fresh water. A major part of thewaterweuse every day is groundwater. Groundwater does not come from lakes or rivers. It comes from underground. The more roads and parking lots we pave，the less water can flow into the ground to become groundwater.

    Human activity is not responsible for all water shortages(短缺). Drier climates are of course more likely to have droughts(干旱) than areas with morerainfall，but in any case, good management can help to make sure there is enough water to meet our basic needs.

    Thinking about the way we use water every day can make a big difference，too. In the United States，a family of four can use 1.5 tons of water a day! This shows how much we depend on water to live，but there's a lot we can do to lower the number.

    You can take steps to save water in your home. To start with，use the same glass for your drinking water all day. Wash it only once a day. Run your dishwasher (洗碗机)only when it is full. Help your parents fix any leaks in your home. You can even help to keep our water supply clean by recycling batteries instead of throwing them away.

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。