| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [verb] [Wh det] | 1924 |
|
| 2 | difficulty [prep] [verb] | 1738 |
|
| 3 | difficulty [prep] [Wh det] | 24 |
|
| 4 | difficulty [verb] [Wh det] | 8 |
|
