c) The Challenger Expedition

The Challenger Expedition, conducted from 1872 to 1876, was the first American-led exploration into the depths of the ocean and a historic milestone in oceanography. The expedition, aboard the HMS Challenger, was the first to systematically study ocean biology, geography, and chemistry. Its findings laid the foundation for the science of oceanography, revealing the vast diversity of life in the deep sea and the physical structure of ocean basins. The Challenger Expedition’s comprehensive collection of data and samples significantly advanced our understanding of the ocean and its ecosystems, marking the beginning of modern oceanographic research.