| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [is] useful [prep] [v-ing] | 72 |
|
| 2 | is useful [prep] [v-ing] | 70 |
|
| 3 | [is] useful for [v-ing] | 40 |
|
| 4 | [is] useful in [v-ing] | 32 |
|
