Grammer ep: 21 Fragments / Run-ons and comma splices

 Fragments don't tell the whole story for example:
"John went to buy marshmallows 4 years ago".  

But a fragment would be "Buy marshmellos".

Now for Run-ons and comma splices:

Comma splices are for separating sentences without punctuation for expensive:

"We bough cookies, and cakes for tea-time". 

Grammer ep: 20 Pronoun-antecedent

Let's take a word: "Peter took his bike to the park, and he rode the swings."

Notice how instead of saying Peter, you can say he since we established that Peter is a guy. 

Now let's take: "The cats ate all the food".

How would we do this since it refers to multiple is: "The cats ate all the food, and they left no trace".