Last month she was explaining to one of her class about sound .这句话有错么
问题描述：
Last month she was explaining to one of her class about sound .这句话有错么
答
One of 后面应该加可数名词的复数，所以应该是one of her classes。 还有就是explained就行了这是过去时不是过去进行时因为last month
答
Last month she explained to one of her class about sound
Last month过去时态的标志
答
Last month she explained to one of her class about sound.
was explainin改为explained
答
explained就行~ 表示已经发生了.
不是强调过去的某个时间点正在做什么事, 不用"was explaining"