| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [vb infin] be several | 6 |
|
| 2 | must [verb] be several | 6 |
|
| 3 | must have be several | 5 |
|
| 4 | must have be several | 5 |
|
| 5 | must [verb] been several | 5 |
|
