The Experimental problem is A. Anna is dead
B. Was Anna murdered?
C. What pill was in Anna’s stomach?
D. Was Anna a drug addict

Explanation:

What is an Experimental Problem? An experimental problem is:

Step One: Right off the bat, we can eliminate A because it's not a question, and an experimental problem is supposed to be a question.

Step Two: Now that we have all questions, we have to figure out which one is too broad. We can eliminate B because although it is not too broad, it is nto specific enough, and is not necessarily science-based.

Step Three: We are between C and D, and the answer is C because it is specifically asking about a pill. In D, it is not necessarily about science, and the question needs to be more specific; it needs to be something that can be explained. With D, it is hard to test, whereas, with C, the main goal is to test.

C is the answer.