run-on sentence is:

A) Always very, very long.
B) Any sentence which is very long and incorrectly punctuated.
C) Two complete sentences joined by a comma rather than a semicolon, conjunction, or period.
D) Two complete sentences joined by a semicolon.
my answer is B but I think it could be A to because run-ons are very very long

Nope.

Look up the definition of "run-on" and "comma splice."

http://grammar.ccc.commnet.edu/grammar/runons.htm

So from my understanding if its not B then it is C

C, yes.

A simple sentence:

A) Can be reversed and still mean the same thing.
B) Expresses one complete thought with one subject and one predicate.
C) Expresses one or more complete thoughts with one or more subjects and one or more predicates.
D) Is easy to understand.
My answer is C

The correct answer to the question is C) Two complete sentences joined by a comma rather than a semicolon, conjunction, or period.

A run-on sentence is a type of sentence that occurs when two or more independent clauses (complete sentences) are joined together incorrectly without proper punctuation or conjunctions. The issue with a run-on sentence is not necessarily the length, although they can often be lengthy.

Option A, "Always very, very long," is not the most accurate definition because run-on sentences can be short or long. It's the incorrect joining of two independent clauses that defines a run-on, regardless of the length.

Option B, "Any sentence which is very long and incorrectly punctuated," is partially correct because a run-on sentence is indeed incorrectly punctuated. However, it does not capture the main problem of two complete sentences being fused together without proper punctuation.

Option D, "Two complete sentences joined by a semicolon," is incorrect because using a semicolon correctly between two complete sentences actually creates a compound sentence, not a run-on sentence.

In conclusion, the most accurate definition of a run-on sentence is C) Two complete sentences joined by a comma rather than a semicolon, conjunction, or period.