例)必要(ひつよう)じゃないのではないだろうか。
What does the writer think?
必要? 必要じゃない?
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Answer: 必要じゃない
When you see A のではないだろうか, focus on A.
The expression often signals the writer’s opinion or inference.
For reading purposes, you can often think of it as “the writer thinks A.”