| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is [adv] difficult [verb] | 830 |
|
| 2 | is often [adv] [verb] | 101 |
|
| 3 | is often difficult [verb] | 80 |
|
| 4 | often [adv] difficult [verb] | 21 |
|
| 5 | is often [adv] difficult | 20 |
|
