| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is [to-vb] [adj] [noun pl] | 615 |
|
| 2 | difficult [to-vb] [adj] [noun pl] | 214 |
|
| 3 | is difficult [to-vb] [adj] | 195 |
|
| 4 | is difficult [to-vb] [noun pl] | 44 |
|
