托福考试

【单选题】
A、The early history of bookbinding.
B．How old books become valuable.
C．Economical ways to protect old books,
D．Why some books deteriorate.

网考网参考答案：D
网考网解析：
What are the speakers mainly discussing document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>