| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is often very difficult [verb] | 7 |
|
| 2 | it is often very difficult [verb] | 7 |
|
| 3 | it is often very difficult [verb] | 7 |
|
| 4 | it is often very difficult [to-vb] | 7 |
|
