This is a difficult passage for text completion. We will solve it using the most appropriate words for most, if not all, options to make a meaningful paragraph.
The best word for the first blank is relations. Oil painting had the same effect on appearance as capital had on social relations.
It reduced everything to the level of objects. So, the second word of option E works but the first word of option D works.
Now, level and equality can be used interchangeably. So, even if it isn’t the perfect word, it fits in the context.
Everything became ‘exchangeable’ because everything was treated as an object or a commodity and measured by its materiality.
Hence, all the words of D work.
Hence, D is the correct answer.