What must a scientist do in order to develop a testable hypothesis? A. Research accepted scientific theories to find one that is wrong.
B. Determine whether the conclusion is supported by popular opinion.
C. Find out whether the idea would be interesting to other scientists.
D. Ask a question that can be answered by making observations.

The correct answer is D. Ask a question that can be answered by making observations.

Explanation:

Basically, in order to develop a testable hypothesis, scientists must adhere to the guidelines of the scientific method.

The scientific method is usually understood to be a so-called hypothetical-deductive method, the core of which is to make hypotheses based on observations or measurements, to make predictions based on them and to check the validity of predictions by repeated experiments. More generally, the scientific method is a general way of obtaining solid knowledge, using many means of proof, both empirical and theoretical, to achieve certainty. The scientific method is a widely recognized tool in the scientific community for seeking objectivity, reliability and transparency in research.

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).