| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] more difficult [to-vb] | 53 |
|
| 2 | become more difficult [to-vb] | 36 |
|
| 3 | [vb past] more difficult [to-vb] | 16 |
|
| 4 | became more difficult [to-vb] | 13 |
|
| 5 | [vb -s] more difficult [to-vb] | 10 |
|
| 6 | becomes more difficult [to-vb] | 9 |
|
| 7 | [v-ing] more difficult [to-vb] | 7 |
|
| 8 | [vb infin] more difficult [to-vb] | 7 |
|
| 9 | prove more difficult [to-vb] | 7 |
|
| 10 | [vb base] more difficult [to-vb] | 7 |
|
| 11 | [vb pp] more difficult [to-vb] | 6 |
|
| 12 | [verb] more difficult to achieve | 5 |
|
