| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [noun] | 120 |
|
| 2 | must have been [noun] | 117 |
|
| 3 | must have been [noun sg] | 47 |
|
| 4 | must have been [noun prp] | 43 |
|
| 5 | must have been [noun pl] | 28 |
|
