| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | which must [vb infin] be | 64 |
|
| 2 | which must have [be] | 64 |
|
| 3 | which must [vb infin] been | 64 |
|
| 4 | which must [vb infin] [been] | 64 |
|
