| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is difficult [verb] | 1529 |
|
| 2 | it is difficult [to-vb] | 1523 |
|
| 3 | it is [adj] to understand | 206 |
|
| 4 | it [be] difficult to understand | 38 |
|
| 5 | it be difficult to understand | 38 |
|
| 6 | it [is] difficult to understand | 37 |
|
| 7 | [pron] is difficult to understand | 31 |
|
| 8 | it is difficult understand | 30 |
|
| 9 | [pers pn] is difficult to understand | 30 |
|
| 10 | it is difficult to understand | 30 |
|
