| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could be [verb] at | 263 |
|
| 2 | could be [vb pp] at | 245 |
|
| 3 | [vb mod] be kept at | 32 |
|
| 4 | [modal v] be kept at | 32 |
|
| 5 | could be kept [prep] | 27 |
|
| 6 | could be kept [prep] | 27 |
|
| 7 | could be kept at | 5 |
|
| 8 | could be keep at | 5 |
|
| 9 | could [be] kept at | 5 |
|
| 10 | could be kept at | 5 |
|
