| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [verb] been [prep] some | 6 |
|
| 2 | must [vb infin] [been] [prep] some | 6 |
|
| 3 | must have [been] [prep] some | 6 |
|
| 4 | must have [been] [prep] some | 6 |
|
