A:①③④
B:④
C:②③④
D:③④
甲: 37 , 21 , 31 , 20 , 29 , 19 , 32 , 23 , 25 , 33
乙: 10 , 30 , 47 , 27 , 46 , 14 , 26 , 10 , 44 , 46
The teachers encourage their students to the problems by themselves, and in this way students can enjoy success.