Final answer:
The crop grown in specially flooded fields or terraces on steep slopes is rice, which has been crucial in feeding large populations due to its high yield and ability to be grown in varied topographies, including terraced mountain regions.
Step-by-step explanation:
The crop that was grown in specially flooded fields or on terraces on steep slopes is C) Rice. Rice cultivation requires flat, submerged fields for optimal growth. These fields are known as paddies. When grown in mountainous regions, rice fields are often found on terraces carved into the slopes, a practice exemplified by the Banaue Rice Terraces, which were created manually by the Ifugao people.
Unlike wheat, which originated in the Fertile Crescent, or maize, also known as corn, which was developed by natives of the Americas, rice has been a staple crop especially in Asian regions, where techniques such as transforming swamp land into usable rice fields led to highly productive agricultural systems. Such systems sustain large populations due to their high yields compared to wheat and other grains.