| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [vb pp] [prep] | 4921 |
|
| 2 | must be [vb pp] [prep] | 4921 |
|
| 3 | [modal v] be [vb pp] at | 3499 |
|
| 4 | must be [verb] at | 249 |
|
| 5 | must [be] [vb pp] at | 229 |
|
| 6 | must be [vb pp] at | 229 |
|
