Step 1: Understanding the Question.
The question asks about the feasibility of conducting model experiments on genetically modified animals to study certain diseases. The goal is to assess which statement is not appropriate for such experiments.
Step 2: Analyzing the Options.
(A) Fibrosis: This is a condition that could be studied in genetically modified animals.
(B) Cancer: Cancer research is commonly conducted using genetically modified animals.
(C) AIDS: Similarly, AIDS can be studied in genetically modified models.
(D) None: Correct — All of the listed options are possible for such experiments, so none of these are incorrect.
Step 3: Conclusion.
The correct answer is (D) None, as all the options are valid for use in genetic modification experiments.