〓学英语学到天亮

阅读是那些已经离开学校的人保持教育的重要方式。
by which 是对的，知所以用by，主要是前面用了way。使用...方式，固定用法by the way of

D.

D.in which
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the way 的用法总结
"the way+从句"结构在英语教科书中出现的频率较高, the way 是先行词, 其后是定语从句.它有三种表达形式:1) the way+that 2)the way+ in which 3)the way + 从句(省略了that或in which),在通常情况下, 用in which 引导的定语从句最为正式,用that的次之,而省略了关系代词that 或 in which 的, 反而显得更自然,最为常用.如下面三句话所示,其意义相同.
I like the way in which he talks.
I like the way that he talks.
I like the way he talks.

当然是D 记住way 做定语从句先行词，关系代词只能是3种 in which that 和 不填

D in which

原因如下：

in……way 用……的方式
in which引导的定语从句，修饰ways。
who has left school也是个定语从句，修饰someone。
remain educated是someone的谓语。

要准确理解这句话，你可以先忽略后面那个定语从句，把这句话改为：
Reading is one of the chief ways in which someone remain educated.

是不是简单了很多？很好理解吧？

选D
way做先行词，做方式状语，之后为定语从句，故其后用in which，或that,或省略不用