The author implies which of the following about natural resources in South China prior to 6,500 years ago? A. Their abundance may have actually served to discourage the development of plant cultivation. B. They were not as abundant as most archaeologists have maintained. C. They led indirectly to cultural contact with peoples from the Yangtze Basin. D. Their importance has been downplayed by scholars studying the beginnings of plant cultivation in South China. E. They had little influence on the types of plants that were eventually cultivated in South China.