| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] to be kept [adv] [adj] | 9 |
|
| 2 | have to be kept [adv] [adj] | 7 |
|
| 3 | [vb past] to be kept [adv] [adj] | 5 |
|
| 4 | had to be kept [adv] [adj] | 5 |
|
