— Is there a ______ as to when I should return the book? 

—  Yes. You have to put it back here no later than next Friday. [ ]

A. boundary

B. limit

C. length

D. degree

2010年上海世博会中国馆“东方之冠”（如图）的主体结构是用国产Q460钢制成的。下列有关Q460钢的性质中，属于化学性质的是

A.强度高

B.能导电

C.耐腐蚀

D.抗震性好