Answer:
B. Scientific Method.
Explanation:
The scientific method is  a way of answering questions, or rather experimenting to build a hypothesis. It had the following steps, observation, forming a question, then hypothesis,  a prediction based on the hypothesis, testing the prediction, and using the results of the test to  adjust the hypothesis if needed, or to make a new one with new predictions.
 
        
                    
             
        
        
        
At “show” trials during the Great Purge, suspects often admitted to fault even when they were completely innocent, in the hopes of receiving a reduced sentence or avoiding the labor camps in the East. 
        
                    
             
        
        
        
Hi, so the rivers provided the a water source that was crucial for the farmers. The farmers provided food and that help sustain the city.