Final answer:
The national rating for Sports Story is 20 percent, calculated by dividing the number of households watching by the total number of households and then multiplying by 100.
Step-by-step explanation:
To calculate the national rating for Sports Story, you would take the number of households that watch the program and divide it by the total number of households in the United States. In this case, 60 million households watch the program out of 300 million households.
The calculation is therefore (60 million ÷ 300 million) × 100 to find the percentage. This equates to 0.2 or 20 percent. Thus, the correct answer is B. 20 percent.