How does the use of いかんによっては in this question determine one answer over another?


In my JLPT practise book, in a section explaining the use of `いかんによっては`, which
roughly means "depending on", they have the following question:

> 学生{がくせい}：先生{せんせい}、台風{たいふう}が近{ちか}づいていますね。明日{あした}のゼミは休講{きゅうこう}ですか？
>
> 先生{せんせい}：そうですね。台風{たいふう}のコースいかんによっては`______`
>
> A: 休{やす}みです。 B: 決{き}めましょう。

I chose the answer B, thinking it roughly meant, "We will decide depending on
the course of the typhoon."

However, according to the book, the correct answer is A, which is translated
as, "depending on the path it might be a holiday." _(The English translations
in this book are not so smooth.)_

Both make logical sense to me, but, despite what the book says, I can't help
but feel that B makes more sense because the path of the typhoon is uncertain,
and therefor so is the decision about the seminar. Thus, "let's wait and
decide."

Why is A the correct answer?




According to 新完全マスター 文法 N3:

> によって：means to change state or behaviour depending on something or according
> to something. It expresses variety and is often used with さまざまだ and かえる.
>
> によっては：pinpoints one outcome from a range of possible outcomes

For the sentence:

そうですね。 台風{たいふう} のコースいかんによっては_________

A: 休{やす}みです。 B: 決{き}めましょう。

A pinpoints one outcome, B does not.

**Note on いかん／いかんによって**

I've got to the correct answer using N3 grammar but I should not really ignore
いかん. It means "what" or "how" so in the above sentence I would say the
expression equates to "depending on what [course]". The impact of adding は to
いかんによって is the same as if added によって.

An alternative way to look at this is to consider いかんによって as one expression,
equivalent to いかんで, which approximates to "in accordance with/is contingent
upon".

The impact of adding は is the same as the difference between いかんで and いかんでは,
which is perhaps easier to workout intuitively.

_References: 新完全マスター文法N3, 日本語表現文型辞典_




As @Axioplase mentioned, the correct answer is A because of the `は`.
`〜いかんによって` does indeed mean "depending on 〜", as does `〜いかんによっては`. However,
using the former kind of speaks on the whole of the multiple possibilities,
usually indicating **that** there is a difference; whereas the latter
enumerates and focuses on just _one_ of the possibilities. Also note that with
the latter, there is usually an implied "maybe" or "might" when translated
into English that isn't explicit in the Japanese (as others have mentioned).

Here are some examples:

### 〜いかんによって

>   * 台風のコースいかんによって市町村の風速や雨量が異なる。 → Depending on the course of the typhoon,
> the amount of rain and wind speed of the different cities will vary.
>   * 所属する党派いかんによって人々が大統領の政策に対しての意見が違うでしょう。 → Depending on which political
> party they belong to, the people's opinions of the president's policy will
> probably differ.
>   * 台風のコースいかんによって企業と施設が開いたり閉まったりする。 → Depending on the course of the
> typhoon, whether it's open or closed will depend on each business or
> facility ("businesses and facilities will be open or closed").
>

### 〜いかんによっては

>   * 台風のコースいかんによっては明日のゼミは休講です。 → Depending on the course of the typhoon,
> tomorrow's seminar might be cancelled. (One possibility of what may happen
> with the seminar).
>   * 所属する党派いかんによっては上司が大統領の政策に同意する。 → Depending on / Because of her political
> affiliation, my boss might agree with the president's policy (One
> possibility of my boss' opinion).
>   * 台風のコースいかんによっては地元の風速が50メートルにも達する。 → Depending on the course of the
> typhoon, local wind speeds may get up to 50 kmh. (One possibility of the
> local wind speeds).
>

It took me forever to understand this difference, but when I did, it gave me a
whole new appreciation for, and outlook on `は.`

