题目

Have you ever wondered why stems(茎)grow upwards and roots downwards? Why do plants always seem to turn towards the light and climbing plants run up rather than down? The answer is simple: auxin(生长素), a chemical substance that controls growth in plants.     Auxin gives away its secrets Auxin is a plant hormone(激素). Darwin was already interested in it in the 19th century. Only in recent years, however, has the hormone started to give away its secrets, thanks to intensive molecular research. Auxin is produced in the young, growing parts of plants and then transported throu关于欧洲西部旅游景点的说法，正确的是（　　）A．英国的峡湾风光引人入胜B．伦敦的艾菲尔铁塔令人景仰C．南部地中海沿岸国家的海滨沙滩优美宜人D．芬兰的花卉尤其是郁金香闻名世界