| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | what had [verb] to | 213 |
|
| 2 | what had [vb pp] to | 213 |
|
| 3 | what had [verb] to | 213 |
|
| 4 | what had happened to | 202 |
|
| 5 | what had happen to | 202 |
|
