| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [verb] been | 3430 |
|
| 2 | must [vb infin] [been] | 3430 |
|
| 3 | must have [been] | 3429 |
|
| 4 | must have [been] | 3371 |
|
| 5 | must 've [been] | 58 |
|
