Final answer:
Floyd Dominy was the leader of the U.S. Bureau of Reclamation in the mid-20th century, responsible for iconic dam projects such as the Hoover Dam. The correct answer is option B).
Step-by-step explanation:
Famous builder of dams, Floyd Dominy, was the leader of the U.S. Bureau of Reclamation (B) in the mid-20th century. The Bureau of Reclamation was significantly involved in developing massive dam projects such as the Hoover Dam on the Colorado River, which was one of the most ambitious engineering feats in U.S. history. This agency also played a crucial role in water resource management in the American West, utilizing advanced technology and large workforces to construct these transformative projects and help regulate water sources like the Colorado River.