阅读下列材料，从每题所给的A、B、C、D四个选项中选出最佳选项。

It's November. If you enjoy relaxing your mind, it's high time to go bird watching. In November, lots of visitors go to Poyang Lake of Jiangxi to relax in a special way. They watch birds. They watch white cranes(白鹤). With the coming of winter, all the birds begin to fly to some warmer places. In early November, a lot of white cranes fly across the sky of Poyang Lake.

    November is not the only time to do the fun thing. In fact, in Jiangxi you can watch birds all the year round. And you can do it wherever you go. Jiangxi is a good place for birds so it has a great many birds. If you keep your eyes open, you will probably find some around you. Here is some advice for bird watching:

● Don't get too close to birds that are building nests (巢) or feeding their babies. Some birds will give up their baby birds if they are frightened.

● Take a pair of binoculars (双筒望远镜) with you so that you can see the birds more clearly.

● Buy a good field (实地) guide if you don't have one yet. It can help you know the birds that you have never seen before.

随着人们环保意识的增强及科学技术的进步，各种绿色环保新产品进入千家万户，今年一月份小楠家将天然气热水器换成了太阳能热水器，减少天然气的用量，去年12月份小楠家的天然气费一共是96元，从今年一月份起天然气费价格每立方米上涨了25%，小楠家2月份的用气量比去年12月份少10立方米，2月份的天然气费一共是90元，请你求小楠家今年2月份用气量是多少？

所谓“人口红利”，是指一个国家的劳动年龄人口占总人口比重大，抚养率比较低，为经济发展创造有利的人口条件，整个国家的经济形成高储蓄、高投资和高增长的局面。读我国的人口红利图，回答下列问题。