| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it must have been | 760 |
|
| 2 | he must have been | 258 |
|
| 3 | she must have been | 137 |
|
| 4 | they must have been | 120 |
|
| 5 | i must have been | 116 |
|
| 6 | you must have been | 87 |
|
| 7 | we must have been | 16 |
|
| 8 | them must have been | 9 |
|
