| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [is] difficult [prep] us [verb] | 17 |
|
| 2 | [is] difficult for us [verb] | 17 |
|
| 3 | [is] difficult [prep] us [to-vb] | 17 |
|
| 4 | is difficult [prep] us [verb] | 13 |
|
