VOA慢速英语:联合国教科文组织称2.9亿学生因新冠病毒留在家中

global – adj. involving the entire world

scale – n. the size or level of something especially in comparison to something else

disrupt – v. to cause (something) to be unable to continue in the normal way

unparalleled – adj. never seen or experienced before

prolong – v. to make (something) last or continue for a longer time

introduce – v. to present (something) for discussion or consideration

cherish – v. to treat with affection and tenderness; hold dear.

challenge – n. a difficult task or problem; something that is hard to do