| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it did [adv] happen | 68 |
|
| 2 | it [vb past] [not/n't] happen | 65 |
|
| 3 | it [vb past] not happen | 65 |
|
| 4 | it [vb past] n't happen | 45 |
|
| 5 | it [vb past] not happen | 20 |
|
