| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb past] [adv] happen | 476 |
|
| 2 | [Wh det] [adv] happen | 337 |
|
| 3 | [vb past] [Wh det] happen | 83 |
|
| 4 | [vb past] [Wh det] [adv] | 57 |
|
