| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | how [verb] [det] happen | 19 |
|
| 2 | how do [adj] happen | 19 |
|
| 3 | how did [adj] happen | 14 |
|
| 4 | how [vb past] [adj] happen | 14 |
|
| 5 | how [verb] this happen | 11 |
|
| 6 | how [verb] this happen | 11 |
|
| 7 | how [verb] that happen | 8 |
|
| 8 | how [verb] that happen | 8 |
|
| 9 | how does [adj] happen | 5 |
|
| 10 | how [vb -s] [adj] happen | 5 |
|
