| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [vb pp] [prep] | 4919 |
|
| 2 | be [vb pp] [prep] [be] | 1857 |
|
| 3 | must be [vb pp] [be] | 42 |
|
| 4 | must be [prep] [be] | 10 |
|
