| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [not/n't] have been | 510 |
|
| 2 | [not/n't] have been [det] | 82 |
|
| 3 | could have been [det] | 63 |
|
| 4 | could [not/n't] have [det] | 30 |
|
