| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [vb pp] [prep] an [adj] | 1268 |
|
| 2 | must be [vb pp] [prep] [adj] | 971 |
|
| 3 | must be [vb pp] [prep] an | 126 |
|
| 4 | must be [prep] an [adj] | 9 |
|
