| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [vb pp] at [art] time | 11 |
|
| 2 | must be [vb pp] at [art] time | 11 |
|
| 3 | must be [vb pp] at the time | 10 |
|
| 4 | must be [vb pp] at the time | 10 |
|
