Laos and Cambodia were drawn into the fighting in Vietnam___. 1. by Communists in those countries
2. when South Vietnam fell to the Communists
3. by the Khmer Rouge
4. when the United States withdrew from Vietnam

answer; /// i believe that one of the causes is (a loss of habitat);

heat from the core of the earth causes convection currents to occur in the mantle. these currents slowly move the crust around.

your answer is 20. hope this !