Mrs. Brown was having a lot of trouble with her skin，so she went to her doctor about it. He could not find anything wrong about her，so he sent her to the hospital for some tests. The hospital，of course，sent the result of the tests to Mrs. Brown’s doctor.

 The next morning he phoned her to give her a list of things that he thought she should not eat，as any of them might be the cause of her skin trouble. Mrs. Brown carefully wrote all the things down on a piece of paper. She then left it beside the telephone while she went out to a party. When she got back home two hours later，she found her husband waiting for her. He had a big basket full of things beside him，and when he saw her，he said，“Hello，dear. I have done all your shopping for you.” “Done all my shopping?” she asked in surprise，“But how did you know what I wanted?”

 “Well，when I got home，I found your shopping list beside the telephone，” answered her husband，“so I went the shops and bought everything you had written down.”

 Mrs. Brown’s doctor sent her to the hospital for some tests because .