Final answer:
The unemployment rate decreases the most between the "High school graduate" and "Some college, no degree" educational levels.
Step-by-step explanation:
The unemployment rate decreases the most when moving between the "High school graduate" and "Some college, no degree" educational levels.
In the given table, the unemployment rate decreases from 5.7% for high school graduates to 5.1% for individuals with some college but no degree. This difference of 0.6% represents the largest decrease in unemployment between consecutive educational levels.
Therefore, the correct answer is option b, "High school graduate" and "Some college, no degree".