【单选题】
Bill Fuller， the mailman， whistled cheerfully as he walked up the hill towards
Mrs.Carter‘s house. His work for the day 31 ， his bag， usually quite heavy
when he started out on his rounds， was empty now 32 the letter that he had to deliver to Mrs.Carter. She lived 33 blocks away， so whenBill had mail for her， he always finished his day‘s work 34 later. He did not 35 this though， because she never failed to ask him in 36 coffee and a piece of her special cake.WhenBill 37 Mrs.Carter‘s house， he was surprised not to find her working in the yarD、She usually 38 her afternoon when the weather was gooD、Bill went around to the back of the house， thinking that she 39 in the kitchen. The door was locked and the curtains were drawn. Puzzled， he returned to the front of the house and knocked loudly on the front door. There 40 .Bill thought that this was very strange because he knew that Mrs.Carter 41 left the house.Just then he noticed that her bottle of milk. Which is always delivered early in the morning， was still on the porch. This 42 him. If Mrs.Carter had not 43 her milk ， maybe she 44 .Bill walked around the house 45 he found an open window. It was a small window， but he 46 to get through . He went into the hall. There he was almost stumbled over Mrs.Carter， who 47 unconscious at the foot of the stairs. Realizing that he 48 get help， he rushed 49 the house， stopped a 50 car and told the driver to go to the nearest telephone and call an ambulance.