| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [modal v] have been | 21560 |
|
| 2 | must have be | 3434 |
|
| 3 | must have [be] | 3434 |
|
| 4 | must [verb] been | 3430 |
|
| 5 | must have [been] | 3429 |
|
