| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | system have [been] a [adj] [noun sg] | 8 |
|
| 2 | system have been a [adj] [noun] | 8 |
|
| 3 | system have [been] a [adj] [noun] | 7 |
|
| 4 | system has [been] a [adj] [noun] | 6 |
|
