What does the passage mainly discuss?
A.Advances in iron processing in the eighteenth and nineteenth centuries
B.The effects of the Industrial Revolution on traditional architectural styles
C. Advantages of stone and timber over steel as a building material
D.The evolution of the use of iron in architecture during the 1800's

_________(54)
A.marks          
B. signs    
C.signals  
D.symbols

_________(53)
A.foreword          
B.preface          
C.complement  
D. index

_________(52)
A.composes  
B.includes  
C.consists  
D.contains

_________(51)
A.explaining   
B. interpreting
C.suggesting 
D.presenting

_________(50)
A.events      
B.stories             
C.facts   
D.materials

_________(49)
A.assists 
B.pays      
C.helps          
D.works

_________(48)
A.antonyms    
B. closest  
C.opposite    
D.controversies

_________(47)
A.evidence                
B.roof     
C.examples    
D.cases

The word "revolutionized" is closest in meaning to _______.
A.quickly started 
B.gradually opened  
C. dramatically changed    
D.carefully examined