| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [not/n't] have [vb pp] this | 19 |
|
| 2 | could not have [vb pp] this | 12 |
|
| 3 | could n't have [vb pp] this | 7 |
|
| 4 | could [not/n't] have done this | 5 |
|
