结核菌素试验的用途有（）

A.用于选择卡介苗接种对象

B.测定宿主的非特异性细胞免疫功能

C.调查结核病的流行情况

D.成人结核病的诊断

E.测定卡介苗接种后的免疫效果

In choosing a friend, one should be very careful. A good friend can help you study. You can have fun together and make each other happy. Sometimes you will meet fair weather friends. They will be with you as long as you have money or luck, but when you are down, they will run away. How do I know when I have found a good friend I look for certain qualities of character, especially understanding, honesty and reliability.
Above all else, I look for understanding in a friend. A good friend tries to understand how another person is feeling. He is not quick to judge. Instead, he tries to learn from others. He puts himself in the other person’s place, and he tries to think of ways to be helpful. He is also a good listener.
At the same time, however, a good friend is honest. He does not look for faults in others. He notices their good points. In short, a friend will try to understand me and accept me.
Another quality of a friend is reliability. I can always depend on a good friend. If he tells me he will meet me somewhere at a certain time, I can be sure that he will be there. If I need a favor, he will do his best to help me. If I am in trouble, he will not run away from me.
There is a fourth quality that makes a friend special. A special friend is someone with whom we can have fun. We should enjoy our lives, and we would enjoy our friendship. That is why I especially like friends who are fun to be with. A good friend likes the same things I like. We share experience and learn from each other. A good friend has a good sense of humor, too. He likes to laugh with me. That is how we share in the joy of being friends. And I know that he is looking for the same quality in me.
When I meet someone who is reliable, honest, and understanding, I know I’ve found a friend!

Which of the following qualities the writer thinks is the most important in choosing a friend

A．Understanding.

B．Honesty.

C．Reliability.

D．A sense of humor.