| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | how do they know | 30 |
|
| 2 | how [verb] they know | 30 |
|
| 3 | how did they know | 17 |
|
| 4 | how [vb past] they know | 17 |
|
| 5 | how do they know | 13 |
|
| 6 | how [vb base] they know | 13 |
|
