Final answer:
A run-on sentence is a sentence in which two or more complete sentences are not separated by any punctuation.
Step-by-step explanation:
A run-on sentence is a sentence in which two or more complete sentences are not separated by any punctuation. To determine which one of the given options is a run-on sentence, we need to look for any punctuation that separates the complete sentences. Option A, 'In 1954, a meteorite hit Ann Hodges inside her own living room,' is not a run-on sentence because it is properly punctuated with a comma. However, Option B, 'Grab another log the fire is dying down,' is a run-on sentence. The two complete sentences 'Grab another log' and 'the fire is dying down' are not separated by any punctuation, making it a run-on sentence.