| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] how long | 36 |
|
| 2 | for how long | 10 |
|
| 3 | for how long | 10 |
|
| 4 | on how long | 9 |
|
| 5 | on how long | 9 |
|
| 6 | to how long | 7 |
|
| 7 | to how long | 7 |
|
| 8 | of how long | 6 |
|
| 9 | of how long | 6 |
|
