| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it be difficult [prep] [noun pl] [to-vb] | 20 |
|
| 2 | it be difficult for [noun pl] [to-vb] | 20 |
|
| 3 | it be difficult for [noun pl] [to-vb] | 20 |
|
| 4 | it is difficult [prep] [noun pl] [to-vb] | 14 |
|
| 5 | it was difficult [prep] [noun pl] [to-vb] | 6 |
|
