The answer is Passive.
Passive, because active would be "The bird left behind seed shells while on the backyard feeder."
2. a mockery
3. abstract
4. an obstruction
2-present participle
3- past
4-present
All people experience birth and death alone.
B.
Life is nothing but an empty dream.
C.
Children are the only path to immortality.
D.
Leave a legacy for others.