Answer:
C. Animal testing is a cruel way to advance the progress of science.
Explanation:
A simple sentence is only one clause that expresses a complete thought, it that has a subject and a verb.
Let's analyze the options:
A. It has presented two conclusions
B. It offers a conclusion based on its reason.
C. It just states one simple idea, with <em>"animal testing"</em> as the subject, and <em>"is"</em> as the verb, with a predicate.
D. it has two clauses