| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been a [noun] | 181 |
|
| 2 | [det] have been a [noun] | 82 |
|
| 3 | [det] must have been a | 24 |
|
| 4 | [det] must have been [noun] | 9 |
|
