D.,
A, B, and C have the solution of the system of Equations (2,1) But D has a solution of (1,2).
        
             
        
        
        
The toothbrush evolved over time and mainly out of necessity. Traces of the first toothbrush can be dated back as early as 3500 B.C.E. These bamboo sticks were then used just like a modern manual toothbrush to clean the teeth. Eventually, the Chinese version of the toothbrush made its way to Europe.
 
        
             
        
        
        
Modern day Iran hope it helps
        
                    
             
        
        
        
Answer:
The rest of this section will be devoted to four types of fronts. Three of these fronts move and one is stationary. With cold fronts and warm fronts, the air mass at the leading edge of the front gives the front its name. In other words, a cold front is right at the leading edge of moving cold air and a warm front marks the leading edge of moving warm air.
When two air masses meet together, the boundary between the two is called a weather front. At a front, the two air masses have different densities, based on temperature, and do not easily mix. One air mass is lifted above the other, creating a low pressure zone. If the lifted air is moist, there will be condensation and precipitation. Winds are common at a front. The greater the temperature difference between the two air masses, the stronger the winds will be. Fronts are the main cause of stormy weather.
hope this helps lol :)
 
        
             
        
        
        
The Reconstruction era was the period from 1863 to 1877 in American history. The term has two applications: the first applies to the complete history of the entire country from 1865 to 1877 following the American Civil War; the second, to the attempted transformation of the 11 ex-Confederate states from 1863 to 1877, as directed by Congress. Reconstruction ended the remnants of Confederate nationalism and ended slavery, making the newly free slaves citizens with civil rights apparently guaranteed by three new Constitutional amendments. Three visions of Civil War memory appeared during Reconstruction: the reconciliationist vision, which was rooted in coping with the death and devastation the war had brought; the white supremacist vision, which included terror and violence; and the emancipationist vision, which sought full freedom, citizenship, and Constitutional equality for African Americans.