| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] difficult [to-vb] | 3607 |
|
| 2 | is [adv] [to-vb] | 3033 |
|
| 3 | is difficult [to-vb] | 1938 |
|
| 4 | is [adv] difficult | 1587 |
|
