| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | hours [noun] | 361 |
|
| 2 | hours [noun sg] | 261 |
|
| 3 | [noun] difficulty | 112 |
|
| 4 | [noun pl] difficulty | 17 |
|
| 5 | hours difficulty | 12 |
|
| 6 | hour difficulty | 12 |
|
