Study the following table and answer the question.
Number of candidates appeared and qualified in a competitive examination from different states over the years.
| State | Year | |||
| 2020 | 2021 | |||
| Appeared | Qualified | Appeared | Qualified | |
| A | 500 | 100 | 600 | 150 |
| B | 600 | 200 | 800 | 250 |
| C | 400 | 50 | 500 | 100 |
| D | 300 | 60 | 400 | 80 |
For which state did the percentage of students qualified did NOT change from 2020 to 2021?
1
C
2
D
3
A
4
B