| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it must have been [noun] | 41 |
|
| 2 | it must [vb infin] been [noun] | 41 |
|
| 3 | it must [verb] been [noun] | 41 |
|
| 4 | it must have been [noun] | 39 |
|
| 5 | it must [verb] been [noun prp] | 27 |
|
| 6 | it must [verb] been [noun sg] | 13 |
|
