| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is [adv] difficult [verb] | 705 |
|
| 2 | it is [adv] difficult [verb] | 558 |
|
| 3 | it is often [adj] [verb] | 214 |
|
| 4 | it be often difficult [verb] | 72 |
|
| 5 | it [be] often difficult [verb] | 72 |
|
| 6 | it [is] often difficult [verb] | 62 |
|
| 7 | [pron] is often difficult [verb] | 59 |
|
| 8 | it is often difficult [verb] | 59 |
|
