| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have to learn | 159 |
|
| 2 | had to learn | 110 |
|
| 3 | have to learn | 97 |
|
| 4 | has to learn | 51 |
|
| 5 | had to learn | 35 |
|
| 6 | having to learn | 17 |
|
| 7 | to have to learn | 8 |
|
