| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [adv] | 562 |
|
| 2 | must have been [det] | 92 |
|
| 3 | have been [adv] [det] | 89 |
|
| 4 | must have [adv] [det] | 9 |
|
