| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is impossible [prep] be certain | 7 |
|
| 2 | it [is] impossible [prep] be certain | 7 |
|
| 3 | it be impossible [prep] be certain | 7 |
|
| 4 | it [be] impossible to be certain | 7 |
|
| 5 | it [be] impossible [prep] be certain | 7 |
|
