Which of the Following Is an Example of a Proximal

Which of the following is an example of a proximal cause?

A) Two psychologically different groups of immigrants settled in two different areas of the same country.Eight centuries later,those two areas still exhibit the same psychological differences.
B) The presence of dairy farming in Europe led people to develop a genetic mutation that digests lactose in milk,while the absence of dairy farming in East Asia meant people did not develop this mutation,leading to lactose intolerance.
C) Living along a continental axis allowed people in the Fertile Crescent to engage in agriculture.
D) An Egyptian pharaoh brought in horse-drawn chariots,which allowed his army to out-maneuver and defeat his enemy in battle.
E) The modern hammer that has evolved over millennia is based on the original rocks that prehistoric humans used as hammers.