Sentence 1: My son fell asleep for his afternoon nap. 
 Sentence 3: The doorbell rang 
 Sentence 4:  I opened the door, but nobody was there 
 Sentence 5:  I closed the door and my son woke up 
 Option 1: I tiptoed through the house so that I wouldn't wake him. 
 Option 2: I tiptoed through the house but my son woke up anyway.