Final answer:
The phrase that BEST describes how a writer can measure the length of the action in his story is elapsed time.
Step-by-step explanation:
The phrase that BEST describes how a writer can measure the length of the action in his story is elapsed time. Elapsed time refers to the amount of time that has passed between two events or actions in a story. It can be measured by looking at the timeline of events and calculating the difference in time between them.
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