| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [Wh det] [modal v] be [adj] | 1582 |
|
| 2 | [pron] [modal v] be difficult | 600 |
|
| 3 | [Wh det] [modal v] [be] difficult | 44 |
|
| 4 | [Wh det] [modal v] [be] difficult | 44 |
|
| 5 | [Wh det] [modal v] be difficult | 44 |
|
