| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb mod] [verb] [is] | 1944 |
|
| 2 | [vb mod] [vb infin] [is] | 1919 |
|
| 3 | [vb mod] happen [be] | 62 |
|
| 4 | [vb mod] happen [is] | 53 |
|
| 5 | [modal v] happen [is] | 52 |
|
