Which of the following is not a factor that has contributed to the rapid population growth

A、Now,therearenowarsandpeopleliveinapeacefulworld.
B、Morechildrencanlivetotheiradulthoodandhavetheirownchildren.
C、Peoplelivelongernowthaninthepast.
D、Peopleimunizemanyfataldiseasesofwhichmanypeopledied.