Okay, this has been bugging me for quite sometimes.
When do we use past participle in active-voiced modifier?
Let me give you an example (from Manhattan SC)"A new textbook focused on recent advances in artificial intelligence was assigned by our instructor."
Let me deconstruct (if I'm wrong, please correct me) this sentence:
Subject = textbook
Verb = was assigned
Modifier to the subject = focused on recent advances in artificial intelligence
Now my question are:
1) Why does the sentence use "focused", not "focusing"?
2) Generally, isn't using past participle in modifier means the modifier is in passive-voice? i.e. "Satisfied by the quality of the work, John proceeded to pay the contractor"
3) Does using "focused" have anything to do with an act of having completed something in the past in this modifier context?