| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have [been] [prep] | 294 |
|
| 2 | must have [been] [prep] | 294 |
|
| 3 | [modal v] have [been] for | 62 |
|
| 4 | must have [be] for | 14 |
|
| 5 | must [verb] [been] for | 14 |
|
| 6 | must have [been] for | 14 |
|
