| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [vb pp] [prep] | 4919 |
|
| 2 | be [vb pp] [prep] [num] | 3992 |
|
| 3 | must be [prep] [num] | 30 |
|
| 4 | must be [vb pp] [num] | 19 |
|
