| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it [vb mod] have [be] useful | 5 |
|
| 2 | it [vb mod] [vb infin] [be] useful | 5 |
|
| 3 | it [vb mod] [verb] be useful | 5 |
|
| 4 | it [vb mod] have [be] useful | 5 |
|
| 5 | it [vb mod] [verb] been useful | 5 |
|
| 6 | it [vb mod] [verb] [been] useful | 5 |
|
