图中4条曲线分别示意北半球中纬度某湖泊的浮游植物生物量与光照、营养物质含量、气温的年变化。若营养物质供应充足，则该湖泊浮游植物大量繁殖大约会持续（    ）

下列各对数中，互为相反数的是（　　）

阅读理解

    Learning English is just like learning to ride a bicycle. When learning English becomes a kind of habit，everything will become easier.

    Please think about how we learned to ride a bicycle. There are four stages (阶段): At the first stage，the child doesn't know what it is to ride a bicycle， nor can he ride. So look at ourselves，when we learned English at the first time， we were also in this condition.

    And then is the second stage. Although the child cannot ride himself，he grows and understands what it is to ride a bicycle. So，at this time，teachers are our navigation (航海) marks.

    So according to this，we are just like the child starting to learn and now come to the third stage. He can ride a bicycle but has to think every time how to do it.

    At last，the fourth stage comes when the child has practiced consciously (有意识地) riding the bicycle so much that he doesn't have to think. Riding a bicycle becomes a kind of habit. He can talk to people and wave (招手) to others while riding.

    Learning English is just like learning to ride a bicycle. When learning becomes a kind of habit，we'll find we can be successful not only in English but also in other subjects. When learning becomes a kind of habit， I think， no， I believe，one day we'll succeed and the success will belong to us forever.

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