• Sally likes to play basketball in the kitchen, but her sister prefers to play soccer in the den.
• Walter wishes he could fly jet planes, but his father wants Walter to keep both feet on the ground.
• Ashley won the election for president, and Susan won the race for queen.

(EXCEPTION, isn't there always an exception??? When both independent clauses are short, you can leave the comma out. How long is "short"? Nobody really knows. My opinion is that short would be three or four words.)

Now, if all conjunctions did was to connect independent clauses things would be very simple indeed. But as you know, conjunctions also connect words, phrases, and clauses. Let's focus for a few minutes on one particular situation with conjunctions: the compound verb. Sometimes the subject of a sentence gets two verbs. For example, in the sentence "The man ate soup and drank milk," "man" is the subject and "ate" and "drank" are the verbs. One subject. Two verbs. Get it? In this case, you DO NOT use a comma. But, if you slip in another subject after the conjunction, then you do use a comma. Watch.

The man ate soup, and he drank milk.

Did you see that???

I just added the word "he" after the conjunction, and all of a sudden I need a comma. If I take the "he" out, I take the comma out too. Watch again.

The man ate soup and drank milk.

Wow!! Now the comma is gone.

(OK. OK. You're remembering the exception above, aren't you. Since both independent clauses are very short, you don't really have to use a comma in either sentence. I kept the clauses short to avoid confusing you. A better example would be something like "The man ate soup from a silver bowl, and he drank milk from a golden goblet." Did you notice the comma?)

Sometimes it is hard to distinguish between a compound sentence (two independent clauses joined by a conjunction) and a sentence with a compound verb. This exercise will give you some practice telling which is which. Remember, use a comma in a compound sentence but not with a compound verb.