| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [be] [prep] two years ' duration | 7 |
|
| 2 | be [prep] two years ' duration | 7 |
|
| 3 | is [prep] two years ' duration | 6 |
|
| 4 | [is] [prep] two years ' duration | 6 |
|
