Confidence is very important in daily life. It can help you to develop a healthy attitude （态度）.A study shows that the people who are more confident are much happier. They can have more chance to make themselves successful. But how to be more confident? Here are some suggestions:
    ·Speak loud   When you are not confident, you can't do well what you want to do. You speak in a voice so low that other people can hardly hear you. Try to speak loud enough so that people can hear you clearly. The .high voice can help you become more confident.
    ·Play sports   Physical exercise makes you tired but completely relaxed. 3 A strong body helps you be full of confidence.
    ·Encourage yourself   Write down a list of things you did during the day to see how many things you have done well. Did you finish your homework? Did you tell a joke that made everybody laugh? Give yourself praise for the good things you've done.
    ·Get rid of （消除） fear   Fear comes along with failure （失败）. But it's easy to overcome （克服） if you know that failure is part of your life. Don't hide your head just because you said something stupid last time. Try to start again and believe you can do better.
    ·Pick up a hobby    If you like singing, sing as much as you can. 4 In some ways, a hobby can make you outstanding. And it will make you happy and confident.

眼球中下列哪个结构含有对光线敏感的细胞（　　）