ANSWERS TO RUN-ON SENTENCE EXERCISE

1. You have to take twelve credits per semester to be considered a full-time student. You will probably need to take at least fifteen per semester, however, if you want to graduate on time.

To correct this run on sentence, you can make it two separate sentences or connect it with a coordinating conjunction: "You have to take twelve credits per semester to be considered a full-time student, but you will probably need to take at least fifteen per semester, if you want to graduate on time." (note that adding the coordinating conjunction meant that the "however" could be removed)

 2. When you first begin writing an essay, you should try not to worry too much about grammar and punctuation. It is more important that you get as many ideas down on paper as you can.

Again, you have two separate sentences here, and they need to be separated with a period after "punctuation."  You could also add a conjunction: "When you first begin writing an essay, you should try not to worry too much about grammar and punctuation because it is more important that you get as many ideas down on paper as you can."

3. John’s new girlfriend is a vegetarian. It’s hard for him because he loves meat.

These are short sentences, but there are still two independent clauses here. It might make even more sense to find a way to connect the two: "John's new girlfriend is a vegetarian, which is hard for him because he loves meat."

 4. More and more women are waiting until they are older to get married. This can make it harder if they want to have children.

  You need a period between "married" and "this."

5. Many democratic voters worry that his association with Bill Clinton will hurt Al Gore; Gore refuses to say anything bad about Clinton, however.

  Correct

6. Fifty-five percent of Americans over twenty-years-old are overweight or obese, and the trend is only getting worse.

  Correct

7. Children should be encouraged to express their creativity this can be done through art, music, or dance. Writing would also be another good option.

  Correct

8. College students sometimes underestimate the importance of being able to write well.  If they are science or math majors they assume they will not need to write after they graduate. 

You need a period between "well" and "If."  Read it out loud and you will hear where the natural pause comes between these two sentences.