The answer is D but I would like to know why it isn't B

The correct answer is D) "has opposed."
The reason "has opposed" is correct is because it matches the past tense context of the sentence. The sentence is discussing the actions and beliefs of the movement "from its beginning," indicating a past period. The phrase "has opposed" correctly conveys that the movement has consistently been against the standardization of taste promoted by fast food chains since its inception.
On the other hand, option B) "opposes" is in the present tense. Using present tense would imply that the movement is currently opposing, which is not accurate in the context of the sentence, as it discusses the movement's historical stance against standardization. Therefore, "has opposed" is the appropriate choice to convey the past action and continuity of the movement's opposition.
If I were to explain it to a 10 year old :
The sentence talks about a group of people who didn't like how all fast food burgers tasted the same, no matter where you got them from.
The correct answer is "has opposed" because it shows that this group has been against this idea for a long time, since the beginning.
"Opposes" would mean they are doing it right now, and not before, which isn't what the sentence is trying to say.
So, "has opposed" fits better because it shows that they've been against it for a while.