| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [v-ing] a | 20914 |
|
| 2 | [prep] [v-ing] at | 2877 |
|
| 3 | [v-ing] at a | 1472 |
|
| 4 | [prep] at a | 58 |
|
