单选题

　　[阅读选择]The ideal battery will store a lot of energy in a small package.Right now， Belcher's model battery， a metallic disk completely built by viruses， looks like a regular watch battery. But inside， its components are very small—so tiny you can only see them with a powerful microscope.

　　Which of the following is true of Belcher's battery mentioned in paragraph 6？

　　A.It is made of metal.

　　B.It is a kind of watch battery.

　　C.It can only be seen with a microscope.

　　D.It is a metallic disk with viruses inside it.