When finished with digging out ancient objects, archaeologists must interpret what they have found.
As far as l know 'V+ing' must be used in this example because we use 'V3' with passive. Am I wrong?
When finished with digging out ancient objects, archaeologists must interpret what they have found.
As far as l know 'V+ing' must be used in this example because we use 'V3' with passive. Am I wrong?
When finished with digging out ancient objects, archaeologists must interpret what they have found.
There is no passive in that sentence.
When finished with digging out ancient objects is an adverbial phrase introduced by when.
Passive would be: The work was finished [by someone, subject=the work].
V3 (here: finished) is merely a past participle, not a passive. It would have the same meaning as: when they are finished with digging out ancient objects, they must etc.
When finished, he left the campus. [adverbial phrase; subject= he]
When finishing his work, he usually drank a cup of coffee. [adverbial phrase, subject=he]
The first means: When he finished.
The second means: when he was engaged in the activity of finishing; it is a noun gerund. These are not verbs with subjects. These are phrases that use verbs forms.