通俗来讲，after是表示动作的先后, since潜在内涵是一个时间段，这只能用after。

A: Some novels become more famous (  ) they are made into movies.

B: Harry Potter is one of them.

A.before  B.after  C.since

【解析】根据题意，只能选择B.after （ A.before 在 ......以前 B.after 在 ......以后  C.since 自从......以来）

A: Some novels become more famous ( after ) they are made into movies.

参考译文：一些小说在它们被拍成电影之后变得很出名。

B: Harry Potter is one of them.

参考译文：哈利波特就是它们一中一个。

解答如下：

B为正确答案

A.before 

(1)介词用法，后面接名词/代词/动名词，在....之前

Annie was born a few weeks before Christmas.  

安妮出生在圣诞节前几周。

Before World War II, women were not recruited as intelligence officers. 

在第二次世界大战之前，女性不能当情报人员。

He spent his early life in Sri Lanka before moving to England. 

在移居英格兰之前，他早年是在斯里兰卡度过的。

Before leaving, he went into his office to fill in the daily time sheet. 

离开前，他到自己的办公室填写了日常考勤表。

(2)连词用法，后面接从句，在...之前 

Before Gallacher could catch up with the ball, Nadlovu had beaten him to it.  

加拉赫还没来得及追上球，纳德洛武就已经抢先一步触到球了。

Be a pupil before you become a teacher.
先做学生,再做老师。

He will come to see you before he leaves Beijing.
他离开北京之前会来看你的。

It will be some time before we know the full results.
还要过一些时间我们才能知道全部结果。

B.after 

(1)介词用法，后面接名词/代词/动名词，在....之后

After 19 May, strikes were occurring on a daily basis.  

5月19日之后，每天都会发生罢工。

After breakfast Amy ordered a taxi. 

早饭后，埃米预订了一辆出租车。

After completing and signing it, please return the form to us in the envelope provided. 

填完表格并签名后，请装进所提供的信封里寄还给我们。

(2)连词用法，引导时间状语从句：后面接从句，在...之后 

After I finished my job,I sat down to read a newspaper.

干完活后我坐下来读报。

After he goes, we shall eat.
他走之后,我们就吃饭。

I'll leave after he comes back.
他回来后我就走。

C.since

(1)引导原因状语从句，“既然”

He must have taken the book since it isn't here.
他一定是把书拿走了,因为书已不在这里了。

Since you can't answer the question, perhaps we'd better ask someone else.
既然你无法回答这个问题，我们最好再问问别人

(2)引导时间状语从句“自从...以后/以来”

Since I left college,I have not seen him.
自从我从大学毕业以后,就没有见过他了。

They have never been to see me since I was ill.
自从我生病之后,他们一直没来看过我。

Since I have owned a bicycle,I have gone to school by it every day.
自从我有了一辆自行车后,我每天骑车上学