| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be used [prep] [det] [noun] | 260 |
|
| 2 | must be [prep] [det] [noun] | 28 |
|
| 3 | must be used [prep] [noun] | 22 |
|
| 4 | must be used [prep] [det] | 11 |
|
