Reading Comprehension

从下列每篇短文的问题后所给的四个选择项中选出一个最佳答案。     

     In a world where everyone is out for themselves, who should we trust? One signal that suggests we are reliable is a smile. Genuine smiles send a message that other people can trust and cooperate with us. People who smile are rated higher in generosity and when people share with each other they tend to display genuine smiles.
     When people do bad things they often smile when they are caught. Is this to their benefit? It can be. We treat people who have broken the rules with more tolerance if they smile afterwards. It does not matter whether it is a false smile, a miserable smile or a real felt smile. They all work to make us want to give the wrongdoer a break. This seems to work because we find people who smile after breaking the rules more reliable than those who do not.
     Sometimes we smile both because it is polite and so that we can avoid feeling bad afterwards. In one study people were asked to remain stony-faced after hearing someone else's good news. They felt bad afterwards and thought the other person would think worse of them as a result. So we nod and smile politely because otherwise we will regret it afterwards. Women, though, seem to feel this pressure to smile at the happy news of others more than men.
     Smiling is one way to reduce the distress caused by an upsetting situation. Psychologists call this the facial feedback hypothesis. Even forcing a smile when we do not feel like it is enough to lift our mood slightly. Although smiling at upsetting things may work, it does not look good to others. When researchers had participants watch distressing videos, those who smiled felt better afterwards than those who did not. But people who smiled at distressing images were judged less likeable by others.