| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [verb] [pron] [verb] | 1319 |
|
| 2 | could [verb] [pron] [vb infin] | 209 |
|
| 3 | [modal v] [verb] [pron] have | 145 |
|
| 4 | could [verb] [pron] have | 143 |
|
