| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | has been [verb] in some study | 6 |
|
| 2 | has been [verb] [prep] some study | 6 |
|
| 3 | has been [verb] [prep] some studies | 6 |
|
| 4 | has been [vb pp] [prep] some study | 6 |
|
