| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [adv] have been [art] [noun sg] | 17 |
|
| 2 | must [adv] have been a [noun sg] | 9 |
|
| 3 | must [adv] have been the [noun sg] | 8 |
|
| 4 | must once have been [art] [noun sg] | 6 |
|
