my hometown is no longer the place

My hometown is not the place_____it used to be.

A 是正解。
My hometown is not the place where it used to be.

place 指的是地方，故用where修饰。

that 定语从句 作从句的宾语
如果改为My hometown is no longer ( ) it used to be twenty years ago 就用what

这里后面的句子做定语，是引导词的选择，从句缺乏宾语，怎样选也应该是THAT，as不能做宾语

my hometown is no longer as the place __as___it used to be
如前面有as, 后面就可用as
这里that = the place

前后都是同一个 place,用that
如果是同一类或者同一性质,用 as

这道题目充分激起了在下当年钻研语法的热情。
翻了两本语法树得到的答案如下：
As引导的定语从句一般指人，物或整个句子的内容。做主语或表语。

My hometown is not (the place as it used to be.)重写后的句子括号内容为表语，因此As是正确的。That也对，用来修饰说明the place。