| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have been [v-ing] [prep] three years | 11 |
|
| 2 | have been [v-ing] for three years | 11 |
|
| 3 | have been [v-ing] for three years | 11 |
|
| 4 | has been [v-ing] [prep] three years | 7 |
|
