(C) for me. Time taken 2:10.
I ended up eliminating all the choices in the first read. Then I soon realised that the "suggesting that experiencing such feelings is a universal human tendency" is a verb-ing modifier modifying the noun it touches "social comparison studies".
(A) The term "schadenfreude" is not the "pleasure". It refers to "pleasure derived from the misery of others."
(B) "them" refers to singular-"schadenfreude".
(C) "schadenfreude" refers to "pleasure derived from the misery of others". "suggesting that experiencing such feelings is a universal human tendency" modifies "social comparison studies". "it" at the end correctly refers to "schadenfreude".
(D) "suggesting that it is a universal human tendency", here "it" seems to be referring to "schadenfreude", so as to mean, "schadenfreude" is a universal tendency. This is incorrect. See how (C) nicely circumvents its way around this issue by incorporating "experiencing such feelings" in its verb-ing modifier.
(E) "Pleasure derived from the misery of others (the term schadenfreude) and social comparison studies were partially validated ..." Really? The meaning is absurd here. You don't need to validate "pleasure" by comparing it to other "people".
So, (C) looks the best choice. Lets wait for the OA.