| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [Wh adv] it is necessary [verb] | 19 |
|
| 2 | [Wh adv] [pers pn] is necessary [to-vb] | 19 |
|
| 3 | why [pers pn] is necessary [verb] | 12 |
|
