Final answer:
Option B is a run-on sentence: 'We usually research things on the Internet, we have packed our encyclopedias and dictionaries away in the attic.'
Step-by-step explanation:
A run-on sentence is a sentence in which two or more complete sentences are not separated by any punctuation. In the given options, option B is a run-on sentence: 'We usually research things on the Internet, we have packed our encyclopedias and dictionaries away in the attic.' This sentence does not have any punctuation separating the two complete sentences, making it a run-on sentence.