The author of the passage mentions which of the following as posing an alternative to the Headland Hypothesis

A． Rain forests have always possessed insufficient quantities of carbohydrate-rich resources to support foragers without the aid of agriculturalists.
B． The difficulty of raising carbohydrate-rich plant species in certain areas of the rain forest may have led to the arrest of those species' co-evolution.
C． Trade relationships between agriculturalists and foragers may have been the cause of the disappearance of certain carbohydrate-rich plant species, not vice-versa.
D． Foragers may have been willing to trade carbohydrate-rich plants in exchange for the more nutritious food products of agriculturalists.
E． Environmental changes in rain forest composition may have led to the loss of certain foraging techniques.