| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been for [pron] | 7 |
|
| 2 | must have been for [pron] | 7 |
|
| 3 | must [vb infin] been for [pron] | 7 |
|
| 4 | must [verb] been for [pers pn] | 5 |
|
