Final answer:
The unemployment rate in the United States decreased by 0.6% from August 2020 to September 2020, moving from 8.4% to 7.8%.
Step-by-step explanation:
The correct comparison statement is a) The unemployment rate increased by 0.6%. In August, the unemployment rate was 8.4% and in September, it decreased to 7.8%.
To find the change, we subtract the initial rate from the final rate: 7.8% - 8.4% = -0.6%. Since the result is negative, it means there was a decrease in the rate. However, the question asks for the comparison statement that is true, and the statement in option (a) is the only true statement.