Answer: A
Explanation: 
Oxygen makes up another 20 to 21 percent of our atmosphere. It's essential for life on Earth, and interestingly enough, it is poisonous when highly concentrated. Our concentration of 20 to 21 percent seems just right.
 
        
                    
             
        
        
        
Answer:
The answer is b) due to an excessive stimulation of smooth muscle in bronchioles. 
 
        
             
        
        
        
Explanation:
To ensure ratification of the document, the Federalists offered concessions, and the First Congress proposed a Bill of Rights as protection for those fearful of a strong national government. The Bill of Rights came into effect in December 1791, after ratification by three-fourths of the state legislatures.
 
        
                    
             
        
        
        
Answer: To help researchers conclude that results are related to the new drug and not to the orange juice. 
Explanation:
I could be wrong, Hope this helps 
 
        
                    
             
        
        
        
Answer:
universities allowed scientist to investigate what they thought even if they were contradicted catholic teachings.