| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have been [v-ing] [prep] [pron] | 981 |
|
| 2 | must have been [v-ing] [prep] | 81 |
|
| 3 | must have been [v-ing] [pron] | 46 |
|
| 4 | must have been [prep] [pron] | 34 |
|
