Linear equations in one variable SAT question

Choice A is correct. It’s given that the rocket contained $467,000\text{kilograms}\text{(kg)}$ of propellant before launch and had $362,105\text{kg}$ remaining exactly $21$ seconds after launch. Finding the difference between the amount, in $\text{kg}$, of propellant before launch and the remaining amount, in $\text{kg}$, of propellant after launch gives the amount, in $\text{kg}$, 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 $\frac{104,895}{21}=4,995$. Thus, an average of $4,995\text{kg}$ 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.