| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] must [be] clean | 5 |
|
| 2 | must [be] [vb pp] clean | 7 |
|
| 3 | must [be] [verb] clean | 7 |
|
| 4 | must [be] keep clean | 6 |
|
| 5 | must [be] kept clean | 6 |
|
