Creating world peace is a rather difficult goal calls for efforts of many generations.A.

问题补充：

Creating world peace is a rather difficult goal, calls for efforts of many generations.

A. one that

B. one

C. that

D. it

答案：

(答案→)A. one that

B. one

C. that

D. it

解析： 考查：one作a rather difficult goal的同位语，后一个分句是定语从句，one做先行词，从句中缺少主语，故用that,句意；创造世界和平是一个非常困难的目标，一个需要许多代人努力奋斗的目标。故选A。