| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it [be] essential for | 90 |
|
| 2 | it [be] essential for | 90 |
|
| 3 | it be essential for | 90 |
|
| 4 | it [is] essential for | 74 |
|
| 5 | it is essential for | 71 |
|
| 6 | it was essential for | 16 |
|
| 7 | it [was/were] essential for | 16 |
|
