There are some kinds of detectives who do not wear a uniform, like Hausman, solve endless mysteries every year. There is, for example, the dust detective. Tiny bits of dust stick to your clothes, your fingernails, your hair, or your shoes. They catch in your nose and in your ears. They tell where you have been and what you have done lately. The dust detective often helps catch a criminal by proving that he has been on the scene of the crime（罪案）.
Then there is the wood detective. By studying a piece of wood he can tell what kind of tree the piece of wood came from. He can tell where it was grown, and how old it is. He can even tell you what the weather was like at a certain place the year Columbus landed in America. The growth rings on a tree tell him.
64．According to the selection, by studying a piece of wood, a wood detective can tell you________.
A．what the weather was like the year Columbus landed in America.
B．what the weather was like last year in the mountain
C．what the weather was like last month in your hometown
D．what kind of tree the piece of wood came from
65．What does the underlined word “they”(para. 1) mean?
A．Your clothes B．Your finger-nail
C．Tiny bits of dust D．Your shoes