Question

您好，我想问您一个英语问题

He will come to call on you the moment he（A） his work.
A. finishes B. had finished C. will finish D. finished
我看见您回答过别人这样一个问题，我也想问这道题，我在其它地方看到说：由连接词if或unless引导的状语从句叫做条件状语从句。当主句是将来时，从句用现在时。
但我不明白的是，这句话没有If 也没有unless,从哪里判断它是条件状语从句呢？
请您帮我解答，谢谢啦。

Answer 1

谁告诉你这个是条件状语从句的啊？？

这是状语从句没错，可是它是时间状语从句啊。

He will come to call on you the moment he（A） his work.

表示时间的状语从句可由when, as, while, whenever, after, before, till (until), since, once, as soon as (或the moment ), by the time, no sooner … than, hardly (scarcely) … when, every time等引导。

e.g. When I came into the office, the teachers were having a meeting.
He started as soon as he received the news.
Once you see him, you will never forget him.

条件状语从句分真实性（有可能实现的事情）与非真实性（条件与事实相反或者在说话者看来不大可能实现的事情）条件句。引导条件状语从句的词（组）主要有if, unless, so (as) long as, on condition that, so (as) far as, if only ( = if )。注意：条件从句中的if 不能用whether替换。

e.g. If he is not in the office, he must be out for lunch.
You may borrow the book so long as you keep it clean.
So far as I know（据我所知）, he will be away for three months.
You can go swimming on condition that ( = if ) you don’t go too far away from the river bank.
If he had come a few minutes earlier, he could have seen her.

Answer 2

the momnet可以看做是一个连词，在现代英语中这种用法很普遍