x=( )
A:1.66
B:6.16
C:9.16
D:4.46
温度/℃
20
30
50
60
80
溶解度
(g/100g水)
K2CO3
110
114
121
126
139
KNO3
31.6
45.8
85.5
169
It's important ________ English well.