| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb mod] have been used | 151 |
|
| 2 | could have been used | 48 |
|
| 3 | may have been used | 35 |
|
| 4 | might have been used | 23 |
|
| 5 | would have been used | 23 |
|
| 6 | must have been used | 11 |
|
| 7 | should have been used | 6 |
|
| 8 | will have been used | 5 |
|
