D. Animal testing should be outlawed due to its lasting and harmful effects on animals.
Explanation:
If you're fighting for animal rights, you can't really go with B, since it defends testing in animals. A and C, on the other hand, don't really defend anything. They are general statements about a fact that could be later on used to support a claim, but are not a claim.
Option D is clearly trying to consider testing on animals a bad thing and therefore, is the best one for the matter.
