Sentence 1: Sam was talking on the phone with his mother. 
 Sentence 3: They had been talking for over an hour 
 Sentence 4:  Sam really wanted to get off the phone wit his mother 
 Sentence 5:  He made up an excuse about how he had to go to class 
 Option 1: The conversation was going on forever. 
 Option 2: The conversation was very boring as they had nothing to talk about.