Which of the sequences below represents the various steels types in order of decreasing hardness?

a. High-carbon > Low-carbon > Medium-carbon
b. Low-carbon > Medium-carbon > High-carbon
c. High-carbon > Medium-carbon > Low-carbon
d. Medium-carbon > High-carbon > Low-carbon
e. Medium-carbon > Low-carbon > High-carbon
f. Low-carbon > High-carbon > Low-carbon