| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [not/n't] [vb infin] been [det] [noun] | 6 |
|
| 2 | could [not/n't] [verb] been [det] [noun] | 6 |
|
| 3 | could [not/n't] have been [det] [noun] | 6 |
|
| 4 | could [not/n't] [verb] been [det] [noun sg] | 6 |
|
| 5 | could [not/n't] have been [det] [noun] | 6 |
|
