C. he intended to show his politeness

D. he would like to thank the old man

3. What is the message mainly expressed in the story?

A. We should learn to be generous.

B. It is honorable to help those in need.

C. People in high positions are not like what we expect.

D. We should avoid judging people by their appearances.

When most of us look at our hands, we might notice that we need to clean, or stop biting our fingernails, and that's about it. But if you ask a doctor, he can see a whole lot more. Everything from poor diet and stress to serious kidney (肾) problems can be revealed by a glance at your fingernails.

　　There are about 30 different nail signs that can be associated with medical issues, though may indicate more than one problem, according to Dr. Amy Derick, a clinical instructor of dermatology at Northwestern University.

　　Here are five of the things a doctor can tell about your health based on your fingernails.

　　1. People who aren't eating well and lack vitamin or dietary may have thinner than normal nails, which are more likely to break.

　　2. Horizontal lines are associated with serious physical stress. They frequently occur in people who have gone through chemotherapy(化疗).They can also occur after some illnesses, injuries, or with severe malnourishment(营养不良).Interestingly, there may be an altitude connection too. They've also been found in people who dove 1,000 feet and others who participated in an Everest exploration.

　　3. Vertical lines, however, are generally not such a big deal. Some people are more genetically prone to them than others, but they're commonly associated with aging.

　　4. When people lack iron, their nails can turn spoon-like. Instead of curving down and covering the finger normally, they 'll start to rise up on the sides and front, like the part of a spoon that holds liquid.

　　5. Kidney and liver problems can create "half-and-half nails", where one part of the nail is white and the other part dark or pink, according to Derick.

Doctors note that because disease diagnosis is complex and some symptoms can be