Sentence Correction

The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart; rather a kind of nuclear battery that uses natural radioactive decay to produce power.
(A) apart; rather
(B) apart, but rather
(C) apart, but rather that of
(D) apart, but that of
(E) apart; it is that of


OG ans is B.Why not C?

Thanks
Peer

the energy source is not 'that of a kind of nuclear battery', it is just 'a kind of nuclear battery'.

that of and kind of together interpret the same thing..so redundant...