There has been the fear ( ) the world will become too crowded to

There has been the fear ( ) the world will become too crowded to accommodate so many people
A、which
B、where
C、about
D、that
【正确答案】：D
【题目解析】：人们担心世界会变得太拥挤，而容纳不下这么多人。fear后应是同位语从句。正确答案是D