A testable hypothesis is a statement that can be supported or refuted through experimentation or observation. Among the options provided, the following is a testable hypothesis:
If acid is added to a solution, then the pH of the solution will go down.
This hypothesis can be tested by adding acid to various solutions and measuring the pH before and after the addition, allowing for clear experimental results.
The other options either involve subjective interpretations (e.g., taste) or cannot be as easily measured (e.g., the bouncing height of a ball), making them less suitable as testable hypotheses.