| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must [be] [vb pp] at [adv] [adj] | 13 |
|
| 2 | must be [vb pp] at [adv] [adj] | 13 |
|
| 3 | must [be] [vb pp] at least [adj] | 10 |
|
| 4 | must [be] [vb pp] at [adv] [num] | 8 |
|
