Answer:
D. There was no more frontier land
Explanation: 
This is the answer because the 1890 census said that the frontier region of the United States no longer existed which means there was no more frontier land. 
Hope this helps!
 
        
             
        
        
        
The Ninth Amendment, or Amendment IX of the United States Constitution is the section of the Bill of Rights that states that there are other rights that may exist aside from the ones explicitly mentioned, and even though they are not listed, it does not mean they can be violated.
 
        
             
        
        
        
The Russian Civil War that broke out after the revolution was between Reds and Whites.
        
             
        
        
        
It would be "Article I" of the Constitution that establishes the legislative branch of the government--since the Founding Fathers wanted to place the largest amount of importance on this branch, since it lies at the heart of the democratic system.