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．