Among" humAnity's CurrEnt proBlEms" (linE 2, pArA. 2), thE ChiEF ConCErn oF thE sCiEntists is______.
A．thE impovErishmEnt oF DEvEloping CountriEs
B．thE Explosion oF thE humAn populAtion
C．thE rEDuCtion oF BiologiCAl DivErsity
D．thE EFFECt oF gloBAl wArming