| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is often [verb] [to-vb] | 11 |
|
| 2 | it is often [vb pp] [to-vb] | 10 |
|
| 3 | it is often used [to-vb] | 6 |
|
| 4 | it is often use [to-vb] | 6 |
|
