A：2.5
B：5
C：10
D：不确定
若分式方程 1x−3+1=a−xx−3 有增根，则 a 的值是（ ）
温度（℃）
20
40
50
60
80
溶解度g
NaCl
36.0
36.6
37.0
37.3
38.4
NH4Cl
37.2
45.8
50.4
55.2
65.6
KNO3
31.6
63.9
85.5
110
169
选用所给单词填空。
went, took, saw
The kindhearted man，who thinks ________his duty to help poor people，is popular with many people who know him.
