Absolutely necessary; something that cannot be done without.
“Supporters insist that public libraries are indispensable to communities without reliable internet access.”
“The author argues that face-to-face meetings remain indispensable, even in a digital workplace.”
In Reading Part 4, one side may call a policy or resource 'indispensable' to strengthen its position, treating it as a non-negotiable necessity. This strong language often marks the writer's firmest claim, useful for identifying the main argument in a summary question.
Synonyms: essential, vital, crucial