Answer:Spectroscopy helps astronomers to determine the composition, temperature, density, and motion of an object.
Infrared spectroscopy helps to identify the atoms and molecules in the object.
The red shift or blue shift (Doppler Effect) in a spectral line tells how fast the object is receding from Earth or coming toward it.
The Doppler shift enables astronomers to discover extrasolar planets.
As a planet orbits its star, the star is alternately moving away from or toward us.
Astronomers can use the Doppler shifts to calculate the speed of the star and the mass of the planet that is tugging on it.
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Option D. Replace a conventional car with an electric car.
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Conventional cars are those which moves with the use of fossil fuels such as petrol and diesel etc while electric cars are those cars which moves with the use of electricity. When fossil fuels burns in the engine of conventional cars, it produces a large amount of smoke which cause pollution in the air while electric cars do not emitt any harmful gases in the environment so electric cars are used instead of conventional cars. 
 
        
                    
             
        
        
        
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D. Success and wealth in buisness and investments.
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There is 50 chance because there are two chromosomes that are same and two which are difeerent . XX MEANs girl XY means boys .