| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it must [prep] be [prep] | 6 |
|
| 2 | it must [prep] be [prep] | 6 |
|
| 3 | it must [prep] been [prep] | 6 |
|
| 4 | it must of be [prep] | 6 |
|
