Which of the following is a scientific hypothesis?

• A. My excessive urination may mean that I have high blood pressure.
• B. Water always boils at 100 degrees Celsius at any altitude.
• C. The Earth is flat.
• D. Exercise reduces blood pressure in hypertensive individuals.

Answer: (A)

A scientific hypothesis is a testable, falsifiable statement about a possible relationship between variables. The claim that excessive urination may indicate high blood pressure fits this idea because it proposes a link between a symptom (polyuria) and a condition (hypertension) that you could test with data. You could study whether people with more frequent urination have higher blood pressure, control for confounding factors, and determine whether the relationship holds or not.

The other statements aren’t as suitable as hypotheses in this context. Saying water always boils at 100°C at any altitude makes an absolute claim about a physical process that isn’t true under real conditions and isn’t a productive testable prediction. Stating that the Earth is flat is a belief contradicted by extensive evidence, and while it could be tested, it’s not a reasonable scientific hypothesis in modern science. The claim that exercise reduces blood pressure in hypertensive individuals is a plausible, well-supported outcome, often treated as established knowledge rather than a fresh, testable prediction.