| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | serve as an | 155 |
|
| 2 | serve as an | 38 |
|
| 3 | serves as an | 33 |
|
| 4 | served as an | 27 |
|
| 5 | served as an | 21 |
|
| 6 | to serve as an | 18 |
|
| 7 | serving as an | 11 |
|
| 8 | serve as an | 7 |
|
