A:don’t know
B:have know
C:haven’t know
D:didn’t know
实验记录如下表
加热时间/min
0
1
2
3
4
温度/℃
沙子
20
25
29
34
38
水
21
22
23
24
I don't believe that ________ little children can finish ________ much work in ________ a short time.