Answer:
it is A I tried to work it out my best have a nice day God bless you
 
        
                    
             
        
        
        
Some isotopes, however, decay slowly, and several of these are used as geologic clocks. Dating rocks by these radioactive timekeepers is simple in theory, but the laboratory procedures are complex. <span>All methods rely on the fact that certain elements (particularly uranium and potassium) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age.</span>
        
             
        
        
        
D) Contour plowing is used to reduce erosion and sediment pollution.
Explanation:
Contour plowing in farming helps to prevent pollution by reducing surface erosion of topsoil and preventing sediment pollution. 
Contour plowing is a farming technique in which crops are planted along the slopes of hills or contoured areas. 
- The rate at which rain water and precipitation moves along slope terrain is very fast. 
- This causes the washing off of the the topsoil on hills to eroded very fast. 
- Contour plowing breaks the slope and farming is done along movement on the contour. 
- This prevents topsoil erosion. 
- It also prevents sediment pollution in nearby streams and water bodies that are located around the valley at the base of the hill. 
Learn more: 
Soil erosion brainly.com/question/2473244
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<span>Accelerating degradation of transboundary ecosystems.
Over exploitation of valuable natural resources.
Soil degradation and increasing sedimentation.
<span>Pollution of water bodies.
   Just to name a few</span></span>
        
             
        
        
        
Explanation:
Heterotroph. 100% correct. Goodluck. glad to help.