| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it must have been one [prep] | 8 |
|
| 2 | it must [verb] been one [prep] | 8 |
|
| 3 | it must [verb] been one of | 8 |
|
| 4 | it must have been one [prep] | 8 |
|
| 5 | it must [vb infin] been one [prep] | 8 |
|
