The indicates an action that will have been completed before another action takes place.
a. present perfect
b. past perfect
c. future perfect
d. past

Do you have any idea how to summarize it ? i'm willing to , but not do it for you.

At midnight thomas edison opened the door and continued his work, but to his surprise it was so late that he had to get some rest. but with his mind racing and his mind at sake he continued working. hours and hours went untill he got it. he had invented the worlds first lightbulb!