| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it be sometimes difficult [verb] | 30 |
|
| 2 | it be sometimes difficult [to-vb] | 30 |
|
| 3 | it be sometimes difficult [verb] | 30 |
|
| 4 | it is sometimes difficult [verb] | 22 |
|
| 5 | it was sometimes difficult [verb] | 6 |
|
