Extending Seed Germination Experiment on Oxygen Requirement

Steps:

• Identify the original experiment's focus: testing seed germination under limited oxygen conditions, likely showing no growth.
• Determine the goal of extension: confirm oxygen's role by manipulating its availability.
• Evaluate choices: select the one that directly tests oxygen as a variable while building on the setup.
• Conclude: introducing oxygen logically follows to observe effects on germination.

Why A is correct:

• Seed germination requires aerobic respiration for energy (ATP production via oxygen-dependent pathways), so adding oxygen tests this essential condition per basic plant physiology.

Why the others are wrong:

• B: Restricting oxygen further repeats the original setup without new insight.
• C: Temperature variation tests a different factor, not directly extending oxygen focus.
• D: Species change introduces unrelated genetic variables, diluting the oxygen hypothesis.

Final answer: A