| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [verb] to | 33 |
|
| 2 | must have [been] [verb] to | 33 |
|
| 3 | must have [been] [vb pp] to | 23 |
|
| 4 | must have [been] [v-ing] to | 10 |
|
