It is answer A and if it's not which im sure it is, it is answer D
In your essay give specific details and don't vague if it is not related to the topic you are writing about, is not important.
Answer:
The two themes which are most developed in Frankenstein are :-
B. The pursuit of technology and the loss of humanity.
D. The meaninglessness of beauty and the joy of friendship.
Hope it helps!