| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [verb] [been] [v-ing] [prep] | 81 |
|
| 2 | [modal v] [verb] [been] [v-ing] about | 22 |
|
| 3 | must [verb] [be] [v-ing] about | 5 |
|
| 4 | must [verb] [been] [verb] about | 5 |
|
