| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [not/n't] [verb] | 21358 |
|
| 2 | could [not/n't] [vb infin] | 21338 |
|
| 3 | [modal v] [not/n't] have | 10578 |
|
| 4 | could [adv] have | 3255 |
|
| 5 | could [not/n't] have | 1782 |
|
