| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is [adv] difficult [to-vb] [subord] | 24 |
|
| 2 | it is [adv] difficult [verb] whether | 18 |
|
| 3 | it is more difficult [verb] [subord] | 6 |
|
| 4 | it is [adv] difficult to know [subord] | 5 |
|
| 5 | it is [adv] difficult know [subord] | 5 |
|
