The answer is San Francisco will be warmer than St.Louis in the winter.
 
        
                    
             
        
        
        
Trading blocs. 
Or Acronyms.
        
             
        
        
        
A. Globalization is the answer
        
                    
             
        
        
        
More than 75 percent
Explanation:
Let us carefully analyze this problem: 
The half life of the rubidium isotope = 50 billion years
    The half-life of a radioactive isotope is the time it takes for it to decay to half of its original amount. 
   Every 50years, we know that a rubidium isotope would split into half. 
Initially when the isotope was formed, we would only have the parent atoms there. There wont be any daughter; 
   ratio of parent to daughter = 100 : 0
When the isotope decays to half; we would have equal number of parent and daughter: 
   ratio of parent to daughter at half life = 50 : 50
The age of the earth is about 4.6billion years; 
 this is;
           
 x 100 = 9.2% of the half-life of the rubidium isotope.
At this time, we should know that only 9.2 percent of the daughter would have been formed. 
The remaining parent would be 100 - 9.2 = 90.8% would still be left undecayed. 
The ratio of parent to daughter  = 90.8 : 9.2 
This is more than 75% of the parent
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Radioactive decay brainly.com/question/10125168
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