| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it had [verb] | 4638 |
|
| 2 | it had [vb pp] | 4333 |
|
| 3 | [pron] had happened | 1350 |
|
| 4 | it have happened | 321 |
|
| 5 | it [verb] happened | 321 |
|
| 6 | it had happen | 171 |
|
| 7 | it [vb past] happened | 157 |
|
