Advocates of animal rights claim that it is ________ to discriminate against animals merely because they are not human.

a.
Racist.
b.
Speciesist.
c.
Trivial.
d.
Moral.

The correct answer is b. Speciesist.

To arrive at this answer, let's break down the question and analyze the options:

a. Racist: Discrimination based on race is a concept that applies specifically to human beings, not animals. Therefore, it does not directly relate to the question.

b. Speciesist: This term refers to discriminating against animals solely because they are not human. It is the most suitable option that aligns with the question.

c. Trivial: This word means something that is unimportant or insignificant, which does not relate to the concept of animal rights.

d. Moral: While morality plays a role in the question, it does not directly address the aspect of discrimination against animals based on their species.

In conclusion, the correct answer is b. Speciesist, as it accurately reflects the concept of discriminating against animals simply because they are not human.