题目

人类的进化可以分为南方古猿、能人、直立人和智人四个阶段，其中生活于我国云南省的元谋人是属于上面四个阶段的             阶段。 答案：直立人      Had he not come an hour earlier, he＿＿＿the secret that his mother was always there.A. must never find 　B．must never have foundC. would never find 　D. would never have found