【单选题】

According to the passage, initial improvement in brain function in Homo’s ancestors resulted at least partially from which of the following

A、the sharing of resources typical of hunter-gatherer groups to which Homo eventually came to belong
B、the freeing of Homo’s heat-sensitive brain from the temperature constraints that had kept its size in check
C、the availability of foods far denser in calories and nutrients than those previously available
D、a rise in Homo’s brain weight relative to his body weight
E、morphological solutions of environmental change developed by the robust proto-humans