Lifestyles of Intensive Hunting and Gathering Groups Living in Permanent

Lifestyles of intensive hunting and gathering groups living in permanent locations remained precarious because

A) they failed to develop better shelters or more secure supplies of food.
B) they failed to increase the size of the hunting and gathering bands.
C) they remained vulnerable to attacks from nomadic groups.
D) they were dependent on particular animals and plants that could disappear if changes in the climate occurred.