Question 17 is based on the passage you have just heard.

    Behind the cash register at a store in downtown San Francisco, Sam Azar swiped his credit card to pay for a pack of cigarettes. （16）The store’s card reader failed to scan the card’s magnetic stripe. Azar tried again, and again. No luck. As customers began to queue, Mr. Azar reached beneath the counter for a black plastic bag.（17）He wrapped one layer of the plastic around the card and tried again. Success! The sale was completed. “I don’t know how it works. It just does.” said Mr. Azar who learned the trick from another clerk. Verifone, the company that makes the store’s card reader would not confirm or deny that the plastic bag trick worked. （18）But it’s one of many low-tech fixes for high-tech failures that people without engineering degrees have discovered, often out of desperation, and shared. “Today’s shaky economy is likely to produce many more such tricks. In postwar Japan, the economy wasn’t doing so great, so you couldn’t get everyday-use items like household cleaners,” says Lisa Katayama, author of Urawaza, a book named after the Japanese term for “clever lifestyle tips and tricks.” So people look for ways to do with what they had. Today, Americans are finding their own tips and tricks for fixing malfunctioning devices with supplies as simple as paper and glue. Some, like Mr.Azar’s plastic bag, are open to argument as to how they work or whether they really work at all. But many tech home remedies can be explained by a little science.

17. How did Sam Azar manage to complete the sale?

原文中提到多次尝试刷卡没有成功后，Sam 拿一层塑料裹在卡上试了一下就成功了，“wrapped one layer of the plastic around the card”，该内容和选项 B）By covering the credit card with a layer of plastic（用一层塑料覆盖信用卡），属于同义替换，故正确答案为 B。