| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it [vb -s] difficult [to-vb] | 43 |
|
| 2 | it become difficult [to-vb] | 24 |
|
| 3 | it [vb past] difficult [to-vb] | 21 |
|
| 4 | it becomes difficult [to-vb] | 20 |
|
| 5 | it seem difficult [to-vb] | 17 |
|
| 6 | it seems difficult [to-vb] | 15 |
|
| 7 | it prove difficult [to-vb] | 14 |
|
| 8 | it proved difficult [to-vb] | 14 |
|
| 9 | it remain difficult [to-vb] | 6 |
|
| 10 | it [verb] difficult to explain | 5 |
|
| 11 | it remains difficult [to-vb] | 5 |
|
