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