the meanings are different. if you just say "northern and southern indian alphabets", then it seems like you're just talking about some northern and some southern indian alphabets - i.e., nothing necessarily complete or exhaustive.
if you use "the", then you're talking about THE alphabets, i.e., all of them.

(the correct way to say this would be "the time at which we were scheduled to meet", since the preposition "at" must be conserved.)

E: if you say "the last day that they are scheduled to collect", this means that "day" must be a direct object.
this makes no sense, unless the employees are collecting days.
"the time that we were scheduled to meet" is incorrect. the literal reading of this (which is the only reading you care about, by the way) is that you were scheduled to meet the time itself.

E：the real problem with choice e involves clarity: 'the last day that they are scheduled to collect' means, literally, that the workers collect days＇

二刷错
后置定语从句that they are scheduled to collect需改为前置定语scheduled。 这是因为，通常，后置定语描述的是名词的暂时属性，前置定语描述的是名词的永久属性或固有属性

老师，想问下如果E前半句改成the last day scheduled to collect,对吗

老师，想问下如果E前半句改成the last day scheduled to collect,对吗

老师，E选项里是不是因为加入that they are scheduled之后，使得to collect这个成分变得既可以成为they are scheduled的状语，又可以理解为require的一个宾补（？还是状语呢）？
还有就是that they are scheduled为什么是定语从句呢？觉得这个从句没有缺成分呀我做题的时候是把它当作了同位语的……/w\

定语前置和后置时的区别：前置定语描述的是名词的永久属性或固有属性；后置定语描述的是名词的暂时属性。

D选项in order to collect做状语修饰require；E选项that they are scheduled to collect做定语修饰day。
不理解collect是什么意思。。。

求D/E解释

根据unlike的平行，直接排除ABC
DE中，E的they指代不明（或指代错误），删