| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] how long | 248 |
|
| 2 | for how long | 122 |
|
| 3 | of how long | 39 |
|
| 4 | on how long | 27 |
|
| 5 | about how long | 18 |
|
| 6 | to how long | 16 |
|
| 7 | at how long | 5 |
|
| 8 | over how long | 5 |
|
