Final answer:
Climate changes have caused several alterations of the Huang River's course over time.
Step-by-step explanation:
The correct answer is d. climate changes. Over time, climate changes have caused several alterations of the Huang River's course.
The Huang River, also known as the Yellow River, is prone to regular flooding and subjecting farmers to recurring cycles of bountiful harvests and natural disasters.
Rainfall around the Yellow River is limited to around twenty inches annually, meaning that the river's floods have usually been paired with periodic droughts.