| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | what used [verb] | 28 |
|
| 2 | what used [to-vb] | 28 |
|
| 3 | what [modal v] to happen | 14 |
|
| 4 | what [vb mod] to happen | 14 |
|
| 5 | [pron] used to happen | 11 |
|
| 6 | [Wh det] used to happen | 10 |
|
| 7 | what used to happen | 9 |
|
| 8 | what used to happen | 9 |
|
| 9 | what used happen | 9 |
|
