| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [adv] [verb] been [det] [noun] | 5 |
|
| 2 | must [adv] [vb infin] been [det] [noun] | 5 |
|
| 3 | must [adv] have been [det] [noun] | 5 |
|
| 4 | must [adv] have been [det] [noun] | 5 |
|
