The infinitive in the given choices are correct in option(A): "To work all night was our only option under the circumstances."
The fundamental form of a verb containing to is the infinitive. It is usually used as a noun, although it can also be used as an adverb or adjective.
Examples include, “to walk,” “to read,” or “to eat.”
Therefore, Option A is the infinitive, "To walk" all night was your only option under the circumstances is the infinitive as it mentions (to walk).
Check out the link below to learn more about infinitive sentences;
https://brainly.com/question/11361558?
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