| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [vb infin] been in a [noun] | 7 |
|
| 2 | must have been in a [noun] | 7 |
|
| 3 | must have been in a [noun] | 7 |
|
| 4 | must [verb] been in a [noun sg] | 7 |
|
