| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | they could [vb infin] | 4286 |
|
| 2 | [vb past] they [vb infin] | 1573 |
|
| 3 | [vb past] they could | 330 |
|
| 4 | [vb past] could [vb infin] | 53 |
|
