I don't know the source of this problem, but the correct answer shouldn't be (D). I don't 100% love any of the choices, but (C) seems to be the best of the bunch.

The problem asks us for a reason why laws are passed that have negative effects on the missionary groups.

In other words, we don't need a reason why these groups are insignificant; if they're insignificant enough, then the laws should have a random effect, or none at all, on them.
We need a reason why laws would deliberately be written with an effect against these groups.

(A) and (D) are essentially the same. They give different reasons, but the point of both of them is, essentially, "These groups don't matter".
That's not a reason to pass legislation against them.

If you had (B) and (E) together, then that combination would be a correct answer.
But (B) alone doesn't show us which group would have more effect on policy decisions, and (E) doesn't establish that the more important groups want anything different from what the missionary groups want. We'd have to have both of these things.

The best choice here is (C), because ...
... it addresses why policy makers ("legislators") would take certain actions, and
... it addresses why those policy makers would see the missionaries in a negative light.

Should be (C).