| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [pers pn] must have been [v-ing] [det] | 8 |
|
| 2 | [pron] must have been [v-ing] [det] | 8 |
|
| 3 | must have been [v-ing] [prep] [det] | 10 |
|
| 4 | must have been [v-ing] [prep] [det] | 10 |
|
