Star A has a spectral type of K and is 20 parsecs from Earth. Star B has a spectral type of K..?

Question

..but it is 100 par-secs from Earth. Both are measured to have the same apparent brightness on Earth. What do we know about these two stars?

Star A is a red giant and Star B is a Main Sequence star

Star A is a protostar and Star B is a T Tauri star

Star A is fusing hydrogen in its core and Star B is fusing hydrogen in a shell around its core.

Star A will emit a planetary nebula before Star B.

which one?

Answer 1

KStar...

Answer 2

This answer is most likely to be correct:

Star A is fusing hydrogen in its core and Star B is fusing hydrogen in a shell around its core.

This answer is probably also correct:

Star A will emit a planetary nebula before Star B.

(Unless, of course, star B is much older than star A.)

This answer is certainly FALSE:

Star A is a red giant and Star B is a Main Sequence star

Without more information, I can't tell you whether this answer is true or false:

Star A is a protostar and Star B is a T Tauri star