| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could have [be] [v-ing] for | 9 |
|
| 2 | could have been [v-ing] for | 9 |
|
| 3 | could have be [v-ing] for | 9 |
|
| 4 | could have [been] [v-ing] for | 9 |
|
