| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | is [prep] four years ' | 15 |
|
| 2 | [is] [prep] four years ' | 15 |
|
| 3 | [is] of four years ' | 14 |
|
| 4 | [is] of four years ' | 14 |
|
