Which of the Following Statements Is the Only One That

Which of the following statements is the only one that could possibly be true about the figure below?
a.
Series X is the labor force participation rate, and series Y is the employment-to-population ratio.
b.
Series X is the employment-to-population ratio, and series Y is the labor force participation rate.
c.
Series X is the labor force participation rate, and series Y is the unemployment rate.
d.
Series X is the employment-to-population ratio, and series Y is the unemployment rate.
e.
Series X is the unemployment rate, and series Y is the labor force participation rate.