| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb base] how difficult it is for | 7 |
|
| 2 | [vb base] how difficult it [is] for | 7 |
|
| 3 | [vb base] how difficult it be for | 7 |
|
| 4 | [vb base] how difficult it [be] for | 7 |
|
| 5 | [vb base] how difficult it [be] for | 7 |
|
| 6 | know how difficult it [be] for | 5 |
|
