Answer :
I think C.Though Humans live there lives unaware, they do know that they will not live forever
Answer:
Though humans live their lives unaware, they do know that they will not live forever.
Explanation:
The excerpt says that "The intellectual side of man already admits that life is an incessant struggle for existence". Your life is already a battle. You're battling to stay alive, at least, every day. You have to eat, drink water and do whatever it takes to maintain a way of receiving the needed resources to survive. Life is a struggle from day 1 and we keep struggling to stay alive until the day we die.