多项选择题 In the part where the author wanted to show us the changeless village life before the installation of the telephone, he chose the details to respectively tell ______.（ ）A.how the villagers lived their changeless life B.how they kept track of time and important events without the help of a watch or a calendar.C.how the villagers came to have a telephone D.what a sensation the installing process created

未知题型 (共用题干) 有五个不同职业人群的冠心病患病率资料，若比较职业不同患病率是否相同。统计学检验的无效假设应是

未知题型 为进一步确诊心律失常的类型Ⅰ应首选