| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is [adj] [prep] [pron] [to-vb] | 329 |
|
| 2 | be difficult [prep] [pron] [to-vb] | 117 |
|
| 3 | [be] difficult [prep] [pron] [to-vb] | 117 |
|
| 4 | [is] difficult [prep] [pron] [to-vb] | 58 |
|
| 5 | is difficult [prep] [pron] [verb] | 43 |
|
