| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have [been] [adv] a | 27 |
|
| 2 | must have [been] [adv] a | 27 |
|
| 3 | must have been [adv] a | 27 |
|
| 4 | must have [been] quite a | 14 |
|
