In the era following the agricultural revolution, changes in climate tended have the greatest effect on peoples who lived mainly by a) nomadic herding. b) sedentary farming. c) long distance trade. d) hunting and gathering.

B) Sedentary farming

When we refer to the "Agricultural Revolution," we're speaking of a time when farming in one place replaced hunting and gathering as the primary means of procuring food.  This was around 5,000 BC, and occurred because farming provided a steady food supply.  However, climate changes had a significant impact on those who relied on farming in a particular place.