| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is difficult [verb] | 1529 |
|
| 2 | it is difficult [to-vb] | 1523 |
|
| 3 | it is [adj] to know | 242 |
|
| 4 | it [be] difficult to know | 104 |
|
| 5 | it be difficult to know | 104 |
|
| 6 | it [is] difficult to know | 87 |
|
| 7 | it is difficult know | 63 |
|
| 8 | [pron] is difficult to know | 62 |
|
| 9 | [pers pn] is difficult to know | 62 |
|
| 10 | it is difficult to know | 62 |
|
