[解析]
71:答案:May 24(th);细节理解题th,可知作者在3月24号有过学校旅行,故填May 24(th);
72:答案:the Dashan Collection House;细节理解题,可知作者去了"大山的藏书楼";
73:答案:(many)pictures;细节理解题,we saw many pictures of the countryside可知作者在艺术室看到了许多照片;
74:答案:four;细节理解题,our eyes were caught by a collection of old photos of the town on the walls of the front hall""we saw many pictures of the countrysid""there were over one hundred different clocks""there was also a stone collection"可知文章提到了4种收藏品.
75:答案:two and a half hour/6.5 hours;细节理解题 in the morning"可知他们在那儿待了两个半小时.