| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is often [adj] [to-vb] the | 49 |
|
| 2 | is often [adj] [to-vb] a | 21 |
|
| 3 | is often difficult [to-vb] [art] | 18 |
|
| 4 | is often possible [to-vb] [art] | 16 |
|
| 5 | is often necessary [to-vb] [art] | 7 |
|
| 6 | is often [adj] to use [art] | 6 |
|
