Which of the following pairs correctly illustrates the difference between a positive and a normative statement?

• A. 'The Earth is round.' and 'The Earth should be flat.'
• B. 'Taxes are high.' and 'Taxes are low.'
• C. 'The sky is blue.' and 'The sky should be green.'
• D. 'The unemployment rate is 5%.' and 'The unemployment rate should be 3%.'

Answer: (D)