| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it be impossible to be [adj] | 30 |
|
| 2 | it [is] impossible to be [adj] | 23 |
|
| 3 | it is impossible to be [adj] | 19 |
|
| 4 | it [be] impossible to be sure | 9 |
|
| 5 | it [was/were] impossible to be [adj] | 7 |
|
| 6 | it was impossible to be [adj] | 7 |
|
| 7 | it [be] impossible to be certain | 7 |
|
