A:③①②④
B:②③①④
C:②①③④
D:③②①④
人们常选用的细菌质粒分子往往带有一个抗菌素抗性基因,该抗性基因的主要作用是( )
Daming did his homework at home.(对划线部分提问)____did Daming ____ at home?