等差数列$\left\{a_n\right\}$前n项和为$S_n$，满足$S_{20}=S_{40}$，则下列结论中正确的是（  ）

读诗《未选择的路》，属于诗人未选择的路的一项是(　　)

某学校的一个生物兴趣小组利用星期天采集了如下图所示植物的标本，请你帮他们完成下列问题．

完形填空

    The summer vacation is the best time for students．They can go outdoors and have fun．They can go to big cities to  1，or go to the countryside to 2the beauty of nature(大自然)．

    Peter is an American middle school student and he loves 3  very much．He always travels in his country．

    This summer vacation he wants to do4．He is interested in Chinese history． 5he is flying to Beijing and Xi'an for the summer vacation．He is leaving on l2th July and 6 New York on the last day of the month．He plans 7 a fantastic vacation．During the 8，he is visiting places of interest and going shopping．At night，he is  9  to enjoy the night views．,He is sure he will have a  10 time．

$\frac{\text{8}}{\text{15}}\times \text{14+}\frac{\text{8}}{\text{15}}$ =____