| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it [be] often difficult [to-vb] [conj] | 6 |
|
| 2 | it be often difficult [verb] [conj] | 6 |
|
| 3 | it [be] often difficult [verb] [subord] | 6 |
|
| 4 | it [be] often difficult [verb] whether | 5 |
|
| 5 | it [is] often difficult [verb] [conj] | 5 |
|
| 6 | it [be] often difficult [verb] whether | 5 |
|
