材料一：古代日本的老渔民发现如果将几条生性活泼的沙丁鱼放入一群被打捞的懒惰的鲇鱼当中，由于好动的沙丁鱼在鲇鱼中乱窜，给鲇鱼带来一定危机感，它们奋力游动，从而避免了由于窒息而亡。这便是有名的鲇鱼效应。
材料二：“商场上没有永远的朋友，也没有永远的敌人”。这蕴含哲理的名言揭示了竞争与合作的辩证关系。美国商界有句名言：“如果你不能战胜对手，就加入到他们中间去。”现代竞争，不再是“你死我活”，而是更高层次的竞争与合作，现代企业追求的不再是“单赢”，而是“双赢”和“多赢”。台湾广告界有句名言：与其被国际化，不如去国际化。 

已知△ABC∽△DEF，△ABC与△DEF的相似比为4：1，则△ABC与△DEF对应边上的高之比为____．

若a^x=3，a^y=2，则a^x+y等于（   ）

王胖子在扬州某小区经营特色长鱼面，生意火爆，开业前5天销售情况如下：第一天46碗，第二天54碗，第三天69碗，第四天62碗，第五天87碗，如果要清楚地反映王胖子的特色长鱼面在前5天的销售情况，不能选择统计____图．

根据短文内容，选择正确答案。
D
    John sent for a doctor because his wife was ill. He called the doctor and made sure they would meet at five. He arrived at the doctor's at twenty to five. He thought. “It s a little bit earlier. I'll wait for a moment. It's good to keep the time. ”
    Then he stopped his car in front of the doctor's. He looked around and saw a noisy square not far from here. He went there and sat down on a chair to enjoy the last light of afternoon sun and make himself quiet. He saw some children playing and some women talking to each other happily.
    Suddenly he heard a girl crying. He came up to her and asked some questions. Then he knew she got lost. John tried to find out her address and took her home. The girl's parents were very thankful.
    Then John hurried to the doctor's. The doctor said angrily when he saw him “You're late. Why did you keep me waiting for 20 minutes?" John said nothing but one word "Sorry!”