Which of the following is a star that is in its old age?
1) red giant
2) brown dwarf
3)black hole
4)protostar

 According my years of Science class, there is a cycle that occurs, and following that cycle, we see that a protostar is at it's earliest stage and a Red Giant as well as a Brown dwarf are middle aged. A black hole is at the end, the second to oldest type of star. Hope it helped!

Which of the following is a star that is in its old age? 1) Red giant

Militarism is the answer.