during the 1980s and 1990s 这句话中,1990s前面要不要加the?加和不加有区别吗

during the 1980s and 1990s 这句话中,1990s前面要不要加the?加和不加有区别吗 one of the effect(s)~,要不要加S啊? 英语翻译the longest river(s)要不要加s These help him start the day.这句话对吗?start要不要加s? what's the telephone number?中number要不要加s? the people's square 的the 到底要不要加? during the summer holidays.为什么要加s? The One Hundred Day Day 要不要加s的? 年前面要不要加“the“ 如in --- 1860s the后面的名词要不要加s,动词呢 children's day 前要不要加the 如果前面有an 后面要不要加s