| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | understand what [was/were] go on | 6 |
|
| 2 | understand what was [verb] on | 6 |
|
| 3 | understand what [was/were] going on | 6 |
|
| 4 | understand what [was/were] [v-ing] on | 6 |
|
