| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is not [verb] for certain | 6 |
|
| 2 | is [not/n't] know for certain | 6 |
|
| 3 | is [not/n't] [vb pp] for certain | 6 |
|
| 4 | is [not/n't] known for certain | 6 |
|
