Its when you dont add commas , periods etc..
example --- the kid went out and play with his friends and he also forgot to come home on time he got in trouble and he cant do anything.
there is many commas missing that is a run on.
Answer:
They are found by the Nazis.
Explanation:
A cat supposedly dropped a book from the book shelf that was closing off the entrance to the annex and the door opened- a Nazi was standing outside and heard it, and soon he took them away
I think the answer is c but I could be wrong!!
I think its c because different things happen and if theres a talking dog it would be an overriding idea i think im right