| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb -s] a [adj] challenge to | 20 |
|
| 2 | [vb -s] a [adj] challenge to | 17 |
|
| 3 | represents a [adj] challenge to | 6 |
|
| 4 | presents a [adj] challenge to | 6 |
|
