| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | was operate | 144 |
|
| 2 | [was/were] operating | 141 |
|
| 3 | were operate | 102 |
|
| 4 | [was/were] operated | 86 |
|
| 5 | [was/were] to operate | 19 |
|
