【单选题】________ wise nation is one good at learning, especially ________ that is good at learning from difficulties.
【单选题】In the late nineteenth and early twentieth centuries, one of the most clearly visible difficulties 【C1】______ teachers in New York schools had to 【C2】______ was how to teach children who did not speak...
【多选题】获取目的基因的方法有多种,下列属于目的基因获取方法的是( )