| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [Wh adv] could it have [vb pp] | 10 |
|
| 2 | [Wh adv] could it have [verb] | 10 |
|
| 3 | [Wh adv] could it have [verb] | 10 |
|
| 4 | [Wh adv] could it have [verb] | 10 |
|
| 5 | how could it have [verb] | 10 |
|
| 6 | [Wh adv] could it have happened | 5 |
|
| 7 | [Wh adv] could it have happen | 5 |
|
