| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it [be] difficult [verb] which | 23 |
|
| 2 | it be difficult [verb] which | 23 |
|
| 3 | it [be] difficult [to-vb] which | 23 |
|
| 4 | it [is] difficult [verb] which | 18 |
|
| 5 | it is difficult [verb] which | 14 |
|
| 6 | it [be] difficult know which | 8 |
|
| 7 | it [be] difficult to know which | 8 |
|
| 8 | it [was/were] difficult [verb] which | 5 |
|
| 9 | it [be] difficult to tell which | 5 |
|
| 10 | it was difficult [verb] which | 5 |
|
| 11 | it [be] difficult tell which | 5 |
|
