| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [vb infin] [pron] have [verb] | 63 |
|
| 2 | [modal v] [vb infin] [pron] have happen | 30 |
|
| 3 | could [vb infin] [pron] [verb] happen | 10 |
|
| 4 | could [verb] [pron] have happen | 10 |
|
