同学你好，该知识点来自沪江网校《新概念英语1、2、3、4册连读【抢学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
Where are you going this afternoon?
这里are going构成现在进行时，但表示将来含义，“将要去……”

are going后面如果加to的话，to是介词，介词后要加名词，比如
We're going to a place called Mont-St-Jean. 我们要去一个叫蒙圣让的地方。

但是这里已经有where作地点状语了，where是疑问副词，副词前不加介词，所以这里没有to。
句子相当于You are going where this afternoon.

are going是现在进行时表示将来，现在进行时可表示将来，主要用于表示按计划或安排要发生的动作。如：
I'm leaving tomorrow. 我明天走。
They're getting married next month. 他们下个月结婚。
Are you meeting Bill this evening? 你今晚将和比尔见面吗？
能这样用的动词不多，常用的有：arrive, come, do, get, go, have, leave, meet, play, return, see, spend, start, stay, wear, work 等。


需要区别的是：
be going to do 属于一般将来时，表示将要做某事。这里to后面要加动词do
Take your seats please. The meeting is going to begin.
坐好吧，要开会了。


this afternoon前是不加in的。

在下列情况下，时间状语前不用介词：

一、当时间状语是today, tonight, yesterday, yesterday morning/ afternoon/ evening, tomorrow, tomorrow morning/ afternoon/evening等时。例如：

There was a play yesterday afternoon.昨天下午有一场戏。

She will be back tomorrow morning.她明天上午回来。

二、由this, that ,these等构成的短语用作时间状语时，其前不用介词。例如：

This term we are going to have a new subject.这学期我们将有一门新的课程。

He didn’t go home that night.那天晚上他没回家。

They are working on the farm these days. 这些天他们在农场工作。

三、由形容词last, next等修饰的名词词组用作时间状语时，其前不用介词。例如：

I saw him in the street sometime last week.上星期我在街上看见过他。

Please come here earlier next time下次请早点来这儿。

四、由every, each等构成的短语用作时间状语时，其前不用介词。例如：

Do you do morning exercises every day? 你们每天做早操吗？

They go to school by bike each day. 他们每天骑自行车去上学。

五、在以“the day(week, month, year)+before/ after…”构成的时间状语前不用介词。例如：

Where did you go the day before yesterday? 前天你去哪了？

They came to this school the year before last. 他们是前年来到这所学校的。

六、在以all 构成的短语作时间状语时，如：all day, all the week, all the year 等前面通常不用介词。例如：

He was busy all day yesterday. 昨天他忙了一整天。

She was ill in bed all the week. 她有病了，卧床整整一个星期。

All that afternoon, I jumped and sang and did all kinds of things. 那天整个下午，我又唱又跳，各种各样的事都做了。


祝同学学习进步~