| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it must [verb] [verb] | 310 |
|
| 2 | it must [verb] [vb pp] | 287 |
|
| 3 | it [vb mod] [verb] occurred | 13 |
|
| 4 | it [modal v] [verb] occurred | 13 |
|
| 5 | [pron] must [verb] occurred | 7 |
|
| 6 | it must [verb] occur | 6 |
|
| 7 | it must [verb] occurred | 6 |
|
