阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。

    Ecotourism is a new term in today's tourism industry. Ecotourism, which is considered as a kind of responsible tourism, is ____ (typical) defined (定义) as travel to places ____ special and unusual plants, animals and cultural heritages (遗产) are the main ____ (attract). It takes ecology and culture into consideration. Therefore, programs ____ (concern) the protection of some natural and cultural spots also form a part of ecotourism.

    Ecotourism is developing ____ great speed. According to a recent report by the World Tourism Organization, ecotourism in recent years ____(enjoy) an annual growth of about 5% worldwide. More than 80 activities have been listed for ecotourism and ____ include bird watching, hiking, diving, photography and taking part in various kinds of local cultural events.

    Big cities are still the major places that attract tourists in our society today. However, it seems some ____ (small) towns and country areas may well become the new destinations for people ____ (visit) tomorrow because they are rich in ecological, cultural and ____ (history) resources.

在一次鼓励创新的课堂上，老师出了这样一道题：给出的四个图形符号(如图所示)，哪个与其他三个的类型不同?有的同学说是图甲，因为它是唯一没有角的图形;有的同学说是图乙，因为它是唯一由直线构成的;有的同学说图丙也正确，因为它是唯一由直线和曲线组成的;还有的同学说，图丁也可以，因为它是唯一非对称的图形。最后，老师的总结是：由于标准和角度不同，这四个图形都可以作为正确答案。答案的丰富多彩表明
 
甲            乙             丙             丁

中央电视台报道,继“食盐加碘”后,我国又将启动“酱油加铁”工程。“酱油加铁”的意义是(  )

①补充人体需要的铁元素

②预防缺铁性贫血病

③改善酱油的味道

④增加黑色素

⑤减少厨房污染物

⑥提高人们的健康水平

下列系谱图中，6号无患病基因，7号和8号婚后生一个同时患两种病男孩的概率是
(　　)

已知数列{}(n=)满足,且当时,. 若, ，则符合条件的数列{}的个数是     （   ）