| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] be [v-ing] a | 435 |
|
| 2 | [prep] be [v-ing] at | 219 |
|
| 3 | [prep] [v-ing] at a | 192 |
|
| 4 | be [v-ing] at a | 53 |
|
| 5 | [prep] be at a | 53 |
|
