Sentence 1: Cathy couldn't understand why her baby had started crying. 
 Sentence 3: She had tried to feed her 
 Sentence 4:  Cathy finally found a hair around the baby's toe 
 Sentence 5:  She was relieved to find that the hair was the culprit 
 Option 1: She had checked her diaper. 
 Option 2: She had checked her the ventilation of the room.