[单项选择]

At this time the state of South Carolina was having hard times. Year after year the soil had been planted with the same crop. It was farmed by uneducated and careless slaves, and the planters knew little about soil conservation. Because the soil was beginning to wear out, crops were smaller.
The younger people were not satisfied to raise cotton on the poor soil of the old South. Many of them moved westward and started cotton plantation (大农场) in Alabama and Mississippi. Moreover, so much cotton had been shipped to factories in England and New England that they had as much cotton as they could use. This brought the price of cotton down. More and more slaves were needed to work on the new and larger plantations, and higher and higher prices were demanded for them. Planters found their expenses rising and their incomes from the sale of cotton reduced. Hard times had come to South Carolina.

Which of the following sentences can summarize the main idea of t
A. Hard times had come to South Carolina.
B. Planters found their expenses rising and their income reduced.
C. The soil was farmed by uneducated and careless slaves.
D. Year after year the soil of South Carolina had been planted with the same crop.