| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [pron] [vb mod] have been difficult | 49 |
|
| 2 | it [vb mod] have been difficult | 48 |
|
| 3 | [pers pn] [vb mod] have been difficult | 48 |
|
| 4 | it [vb mod] have been difficult | 48 |
|
| 5 | [pron] would have been difficult | 38 |
|
| 6 | [pron] must have been difficult | 7 |
|
