These are scenarios where it's difficult to build, our current construction techniques don't work, it's too large, it's too dangerous, it's expensive, too many parts.
組み立てが困難な環境下では 現行の建設技術は役に立ちません 大き過ぎたり 危険過ぎたり 高価過ぎたり 部品が多過ぎたりするからです