一个精密零件，实际长5毫米，要图纸上得到10厘米的长度，这张图纸的比例尺是[ ]

A．2：1    

B．20：1    

C．1：20

You may keep this book for a month, _____ you don'  t have it lost.[ ]

A. as well as  

B. as well

C. as long as  

D. as far as