Working on Fossiliferous Strata in the Mountains of Western Italy

Working on fossiliferous strata in the mountains of western Italy, ________ was first to work out ________, which is the fundamental way geologists know which bed is older in any sedimentary sequence.

A) James Hutton, the principle of uniformitarianism
B) Charles Lyell, the sequence of orogenies
C) William Smith, the principle of fossil succession
D) Nicolaus Steno, the law of superposition