Improve the highlighted part of the sentence given below.
Why the dinosaurs died out $is\, not\, known.$

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Most donors would seriously $protest$ any effort to extrapolate from such limited data.

Improve the highlighted part of the sentence given below.
You are warned $against\, committing$ the same mistake again.

Improve the highlighted part of the sentence given below.
This telephone number $is\, not\, existing.$

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The poor villagers $have\, waited$ in the bitter cold for more than $4$ hours now.

Improve the highlighted part of the sentence given below.
Realising the significance of technical education for a developing country,the government $laid\, aside$ a large sum on it during the last plan-period.