| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be required to | 193 |
|
| 2 | is required to | 60 |
|
| 3 | be required to | 44 |
|
| 4 | are required to | 42 |
|
| 5 | were required to | 21 |
|
| 6 | was required to | 20 |
|
| 7 | been required to | 6 |
|
