6Theworld’spopulationisoneofthebiggest_________(challenge)oftheworldtoday.
2021-12-13 50次 反馈错误 加入收藏 正确率 : 100%
题目内容：
6The world’s population is one of the biggest_________(challenge) of the world today.
优质解答
Challenges 加上s.以后要知道了,凡是one of...后面的东西是复数形式.
本题链接：
