Final answer:
The significant prehistoric root crop of Southeast China was rice. Evidence from archaeological sites in modern Hunan province suggests that rice cultivation began as early as 7500 BCE.
Step-by-step explanation:
The significant prehistoric root crop of Southeast China was rice. Evidence from archaeological sites in modern Hunan province suggests that rice cultivation began as early as 7500 BCE. The people living in this region cultivated wild rice and developed sophisticated techniques for growing and harvesting it. Rice became a staple crop in Southeast China and played a crucial role in the development of ancient Chinese civilization.