题目

对于一个基因的正确描述是 ①基因是DNA分子上特定的片段             ②它的分子结构首先由摩尔根发现 ③它决定某一遗传性状或功能                   ④它的化学结构不会发生变化 A．①②                             B．①③                      C．③④                      D．①④________ 200 students went for the picnic, ________ some from No．4 Middle School．A.Totally; includesB.In total; includedC.Total; includingD.In total; including