| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [verb] [prep] some | 10 |
|
| 2 | must have been [verb] [prep] some | 10 |
|
| 3 | must have been [verb] [prep] some | 10 |
|
| 4 | must have been [vb pp] [prep] some | 8 |
|
