Good Riddles

Question: If 1+1=2, 2+2=8, 3+3=18. What does 4+4=?

Question: There are two persons. One is dead and one is still breathing. The dead one is called dead person. What did the other person call?

Question: If we breathe oxygen in morning what do we breathe at night?

Question: What has rivers but no water, forest but no trees and cities but no people.

Question: I am life without death, death without life, a world with no space, space with no world What am I?