Why choose 見てからでないと in this question?


I came across the following question when preparing for the N2 exam:

> マンションを買うときは実際に＿、心配だ。
>
> a 見た上で b 見て以来 c 見てからでないと

I thought the answer is a but it's given as c.

That doesn't seem to be right since it's explicitly stated that for this
construction,

> 後には、否定的な意味の文がくる

which 心配だ doesn't seem to fit.

Is the answer wrong or maybe I didn't understand the sentence.




So, I'm not entirely sure why you think

> 後には、否定的な意味の文がくる

Doesn't fit with option `c` here. This just says that you can expect the
grammar in question to be followed by something with a negative meaning; it's
not for example suggesting that there has to be a [negative
conjugation](https://jisho.org/search/%E5%90%A6%E5%AE%9A%E5%BD%A2) involved.
`心配` may literally mean worry, but it's being used here to express the fact
that something is a bad idea - which seems negative enough to me.

However, it's kind of a moot point in this case anyway because the other two
options don't really make sense.

> マンションを買うときは実際に見た上で、心配だ。
>
> When (someone is) going to buy an apartment, (I) worry about it after
> (they've) actually seen it. (?)
>
> マンションを買うときは実際に見て以来、心配だ
>
> When (someone is) going to buy an apartment, (I) worry about it since
> (they've) actually seen it. (???)
>
> マンションを買うときは実際に見てからでないと、心配だ
>
> When (one is) going to buy an apartment, (I) worry about it unless (they
> are) buying after having seen it.

It's pretty awkward to try and provide direct translations for these sentences
because it's impossible to place all these implied subjects without more
context, but if it helps you, here is a much more natural English translation
for option `c`.

> When shopping for apartments, it's not a good idea to buy something you
> haven't seen first.




So, I'm not entirely sure why you think

> 後には、否定的な意味の文がくる

Doesn't fit with option `c` here. This just says that you can expect the
grammar in question to be followed by something with a negative meaning; it's
not for example suggesting that there has to be a [negative
conjugation](https://jisho.org/search/%E5%90%A6%E5%AE%9A%E5%BD%A2) involved.
`心配` may literally mean worry, but it's being used here to express the fact
that something is a bad idea - which seems negative enough to me.

However, it's kind of a moot point in this case anyway because the other two
options don't really make sense.

> マンションを買うときは実際に見た上で、心配だ。
>
> When (someone is) going to buy an apartment, (I) worry about it after
> (they've) actually seen it. (?)
>
> マンションを買うときは実際に見て以来、心配だ
>
> When (someone is) going to buy an apartment, (I) worry about it since
> (they've) actually seen it. (???)
>
> マンションを買うときは実際に見てからでないと、心配だ
>
> When (one is) going to buy an apartment, (I) worry about it unless (they
> are) buying after having seen it.

It's pretty awkward to try and provide direct translations for these sentences
because it's impossible to place all these implied subjects without more
context, but if it helps you, here is a much more natural English translation
for option `c`.

> When shopping for apartments, it's not a good idea to buy something you
> haven't seen first.

