Sentence Correction

The stars, some of them at tremendous speeds, are in
motion just as the planets are, yet being so far away
from Earth that their apparent positions in the sky do
not change enough for their movement to be observed
during a single human lifetime.
(A) The stars, some of them at tremendous speeds,
are in motion just as the planets are, yet being
(B) Like the planets, the stars are in motion, some
of them at tremendous speeds, but they are
(C) Although like the planets the stars are in motion,
some of them at tremendous speeds, yet
(D) As the planets, the stars are in motion, some of
them at tremendous speeds, but they are
(E) The stars are in motion like the planets, some of
which at tremendous speeds are in motion but

The OA is B and can be eaisly identified by POE.

My question is in B, they is a subjective pronoun and Them is an objective pronoun, and the subject of the sentence is The stars, so how can both They and Them refer to the stars.

Thanks,

Vineet