The main reason why Alexis de Tocqueville traveled to the united states was to observe American democracy in action, and to take note of what worked and what didn't, as many European countries were going through democratic revolutions of their own.
So, the third one.
 
        
             
        
        
        
United States bombing Nagasaki
        
                    
             
        
        
        
Even though the Roman republic existed for many centuries anxiety and unrest within the government start to test it apart, Also civil war commenced between diverse groups with different loyalties.
The role Caesar played in weaking of the republic and the birth of the empire was that he helped resuscitate order, then seized power. His occupation of Rome and his rule as a dictator successfully ended the republic.
Explanation:
 
        
                    
             
        
        
        
The Montreal Protocol, the Clean Air Act , Clean Water Act are taken to protect the environment. 
Explanation:
Private citizens can play important role in managing the environment such as , firstly they can reduce the products, reuse the products and the recycle the products. Plastic bottles will be a good example of reusing of products, grocery bags can be a good example of recycling products and use of cycle instead of motor vehicles can be used as reduction of products because if we reduce use of motor vehicles it will help in reducing pollution.
 Private citizens can try to conserve water so that the ground water level do not reduce. Private citizens should be rational , provide education to people so that they can understand the good and bad things. Private citizens should become proper volunteers to look after the environment. They should plant more trees to keep our environment clean.