b. Run-on
Run-on sentences are when two or more complete sentences (also called independent clauses) are not separated properly by a period, a semicolon, a coma or are not joined by a conjunction, which makes the sentence grammatically faulty.
The passage given is an example of that as its parts are not connected correctly and the idea does not flow naturally. One way we can connect the clauses of the sentence correctly is by using conjunctions and commas:
I know the classics are important, however, I read mostly modern novels because I think modern literature is more interesting.
