| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [subord] [v-ing] at a | 5 |
|
| 2 | [prep] [subord] [verb] at a | 5 |
|
| 3 | [prep] [subord] at a [noun] | 9 |
|
| 4 | [prep] [subord] at a [noun sg] | 7 |
|
