A scientist notes that ornamental grass grown in a creek bed is taller than the same type of grass grown on the creek bank. The scientist suspects that this difference is due to water availability. This proposed explanation is a(n)

• A. Theory
• B. Observation
• C. Fact
• D. Hypothesis

Answer: (D)

In science, a hypothesis is a testable explanation for an observed pattern that can be investigated with experiments or further observations. Here, the scientist notices that ornamental grass is taller in a creek bed and proposes that water availability is responsible. That proposed explanation is a hypothesis because it makes a specific, testable claim about cause and effect that researchers can evaluate by manipulating water levels and controlling other factors to see if growth changes. If more water consistently leads to taller grass under controlled conditions, the hypothesis gains support; if not, it would be revised or rejected. This idea differs from a fact, which is an observed statement that is verified, and from a theory, which is a broad, well-supported framework that explains many related phenomena after extensive testing.