Marie has written this paragraph in support of a research paper.
1) animal testing remains controversial, with passionate views on both sides of the debate. 2) many americans support it, arguing that it provides medical knowledge it would be unethical to obtain any other way. 3) others believe that animals have essential rights that are violated when they are subjected to the inhumane conditions of vivisection. 4) this practice is problematic for many.
which sentence, if placed between sentences 3 and 4, would most improve the clarity of the paragraph?
a. they cite the work of philosopher peter singer in their arguments.
b. vivisection is medical experimentation on a living animal.
c. this opposition to all forms of testing, however, is a minority view.
d. the practice was widely accepted until the 20th century.