| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb past] [vb pp] [pron] could | 91 |
|
| 2 | [vb past] [vb pp] [Wh det] [modal v] | 21 |
|
| 3 | [vb past] [verb] [Wh det] could | 17 |
|
| 4 | [verb] [vb pp] [Wh det] could | 14 |
|
