Whats the answer for number 20?

Your answer is A. New transportation systems.

Hope this is one of the answers you needed help on.  ^▽^

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あなたの答えはAです。新しい輸送システム。

これがあなたが助けを必要とした答えの1つであることを願っています。 ^▽^

the answer is a glaciers carved a large valley that later flooded and became puget sound

the difference is that white collar worker performs skills like worker as a scientist or well blue collars do physical work and they do services like being a cook.