Raising the retirement age to 70 would keep experienced Americans in
their jobs longer. However, it would take jobs away from younger
Americans.
Indeed is when you agree with something, but here we are making a contradiction by stating something that would occur if we increase the retirement age.
For instance is when you are giving an example, which we are not doing.
Finally is for when you are need a word to end a chronological sentence, that is not happening here.
This means the only option left is B) However.
I hope this helps! :)