| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | could [adv] be maintain | 14 |
|
| 2 | could [adv] be maintained | 14 |
|
| 3 | could not be maintain | 9 |
|
| 4 | could [not/n't] be maintain | 9 |
|
| 5 | could not be maintain | 9 |
|
| 6 | could [adv] be maintain | 5 |
|
