A union of two people that is recognized both legally/spiritually (under God if you're into religion).
Answer:
The answer would be the second sentence;
The old oak tree in our backyard is covered in gnarled branches.
Explanation:
None of the other sentences correctly use the word "gnarled".
Answer:
A sacrifice is giving up something for the greater good of something
dude just bs your way through or use like book examples like when harry gets himself "killed" for the greater good of slaying the horuxes and defeating voldemort