Final answer:
The given sentence is a run-on sentence because it includes several independent clauses without correct punctuation. It could be corrected by splitting into separate sentences or using a semicolon and a conjunction for clarity. The correct answer is option: C. run on
Step-by-step explanation:
The sentence in question, "Tomorrow is just another day on a calendar or so I thought but then I found out it was Christmas," is an example of a run-on sentence. It contains multiple independent clauses without proper punctuation between them. A run-on sentence could be revised by making each independent clause into a separate sentence, by adding a coordinating conjunction, or by the use of a semicolon.
For instance, a corrected version could be: "Tomorrow is just another day on a calendar, or so I thought. But then, I found out it was Christmas." Or it could be written using a semicolon: "Tomorrow is just another day on a calendar; however, then I found out it was Christmas." These revisions prevent the run-on and improve the clarity of the sentence.