Sentence Correction

Below are couple of questions whose solutions in the OG were hard to grasp.Could someone help me understand the solutions?

79. Ryonosuke Akutagawa's knowledge of the literatures
of Europe, China, and that of Japan were instrumental
in his development as a writer, informing his literary
stvle as much as the content of his fiction.
(A) that of Japan were instrumental in his
developmentas a writer, informing his literary
style as much as
(B) that of Japan was instrumental in his
development as a writer, and it informed both
his literary style as well as
(C) Japan was instrumental in his development as a
writer, informing both his literary style and
(D) Japan was instrumental in his development as a
writer, as it informed his literary style as much as
(E) Japan were instrumental in his development as
a writer, informing both his literary style in
addition to

In this question, I'm sure about A,B and E being incorrect. However, I can't understand why C is better than D.


74. Despite its covering the entire planet. Earth has a
crust that is not seamless or stationary, rather it is
fragmented into mobile semirigid plates.
(A) Despite its covering the entire planet, Earth has
a crust that is not seamless or stationary,
rather it is
(B) Despite the fact that it covers the entire planet,
Earth's crust is neither seamless nor is it
stationary, but is
(C) Despite covering the entire planet, Earth's crust
is neither seamless nor is it stationary, but
rather
(D) Although it covers the entire planet, Earth's
crust is neither seamless nor stationary, but
rather
(E) Although covering the entire planet, Earth has a
crust that is not seamless or stationary, but

Isn't it awkward and wordy to use "but" and "rather" together?

Thanks,
Nikhil