OG详解-OG2 数学1 Q10

Choice A is correct. It’s given that the rocket contained 467,000 kilograms (kg) of propellant before launch and had 362,105 kg remaining exactly 21 seconds after launch. Finding the difference between the amount, in kg, of propellant before launch and the remaining amount, in  kg, of propellant after launch gives the amount, in kg, of propellant burned during the 21 seconds: 467,000 - 362,105 = 104,895 . Dividing the amount of propellant burned by the number of seconds yields 104,8952121​= 4,995 . Thus, an average of 4,995 kg of propellant burned each second after launch.
Choice B is incorrect and may result from conceptual or calculation errors. 
Choice C is incorrect and may result from conceptual or calculation errors. 
Choice D is incorrect and may result from finding the amount of propellant burned, rather than the amount of propellant burned each second.