| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun sg] or [verb] at a | 15 |
|
| 2 | [noun] or [verb] at a | 12 |
|
| 3 | [noun] or [v-ing] at a | 8 |
|
| 4 | [noun] or [verb] at an | 5 |
|
