模块独立性是软件模块化所提出的要求，衡量模块独立性的度量标准则是模块的( )。A

Dear Ms. Donforth,                                            
     I'm writing to ask you come to our class for a visit. I've   
heard that you have been to Greece. On our Greece unit, we    
have been learning about it's rich culture and long history. 
Since you have visited Greece several times. So I would like to
know whether you have seen the old buildings here. We have    
learned a lot from the textbook, but I believe you personal   
experience will be a lot better. Your knowledges of Greece can
help the whole class. Could you share your experiences for    
us? It will be surely exciting and rewarding. I hoped that you
think about my request and visit us as soon as possibly.     
Sincerely.                                                    
Jeremy Taylor