| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | which [is] useful [prep] [v-ing] | 6 |
|
| 2 | which is useful [prep] [verb] | 6 |
|
| 3 | which [is] useful [prep] [verb] | 6 |
|
| 4 | which [is] useful [prep] [verb] | 6 |
|
| 5 | which [is] useful for [verb] | 6 |
|
| 6 | which [is] useful for [verb] | 6 |
|
