How to determine the scope of modifiers in long sentences?

Question

I found a difficulty to determine the scope of modifiers in long sentences. To make it clearer, see the following sentences. My translation may be wrong.

Sentence 1

新しい工場を建てるに当たって（は）、環境への影響などを調べ、地域の人々と話し合う機会を持つ必要がある。

Prior to building a new factory, it is necessary to have an opportunity to

• investigate things like its effect on environment, and

• speak with the people in that region.

Here I assume that 環境への影響などを調べ、地域の人々と話し合う is the modifier of 機会.

Sentence 2

進学に当たって（は）、学校を見学したり、先輩に話を聞いたり、先生に相談したりして、できるだけ選択肢を広げて考えることが重要だ。

Prior to entering a higher school, the necessary things are

• to do things like observing the school, listening to stories from seniors, discussing with teachers,

• to widen the alternatives as much as possible, and

• to think.

Here I assume that 学校を見学したり、先輩に話を聞いたり、先生に相談したりして、できるだけ選択肢を広げて考える is the modifier of こと.

Questions

How to determine the scope of modifiers in long sentences?

Answer 1

As for Sentence 1, there are two possible ways to parse this sentence.

• 「環境への影響などを調べ、地域の人々と話し合う」 as a whole modifies 機会, as you guessed.
• First 「環境への影響などを調べ」, and then, 「地域の人々と話し合う機会を持つ」. That is, 機会 is modified only by 「地域の人々と話し合う」.

But whichever way you read it, it doesn't considerably change the meaning.

Sentence 2 is more complicated, because there is one more nesting. Read this sentence like this:

Prior to entering a higher school,
{
    thinking while/after widening your choices as much as possible, ← BY {
        - observing the school
        - listening to stories from seniors
        - discussing with teachers
    }
} is important.

Do you remember the "歩いて学校に行く" pattern I mentioned before? (歩いて describes how you 学校に行く.) Here, the 「～たり～たり～たりして」 part describes how you 「できるだけ選択肢を広げて考える」. And the 「できるだけ選択肢を広げて」 part describes how you 「考える」. And as you said, 「～たり～たり～たりしてできるだけ選択肢を広げて考える」 modifies こと.

Unfortunately, there is no easy way to parse long sentences. It's often impossible to parse them without your common sense and background knowledge, and more importantly, practice.