Read the claim.
animal testing is unnecessary in this century and should be banned.
read the counterclaim.
animal testing has led to important medical breakthroughs.

which is the best rebuttal to address the counterclaim?

with modern technology, scientists can make advances without involving the one hundred million animals now used each year for animal testing.
with over one hundred years of successful animal testing, it is obvious that the scientific community must go on using animals to continue to be successful.
while it is true that there have been successes in the past with animal testing, that is not necessarily an indicator of what will happen in the future.
while animals have been used for testing throughout history, this does not mean that people should just keep doing that because they are used to it.