| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is [adv] difficult [prep] us | 5 |
|
| 2 | it is [adv] difficult [prep] us | 5 |
|
| 3 | it is difficult [prep] us [verb] | 12 |
|
| 4 | it is difficult [prep] us [to-vb] | 12 |
|
