kinetics - Does the initial rate in the reaction of magnesium powder with nitric acid depend on the volume or the concentration of the acid?

For the question regarding the initial reaction rate, I don't quite understand why the answer is D.

If I calculated the number of moles from the volume and conc, I would get A=0.4 moles; B=0.2 moles; C=0.2 moles; D=0.1 moles

As original equation is 0.2 moles of NH3, at 25 degree Celsius, I chose C. But why is the answer D, given that it is 0.1 moles not 0.2 moles.

Thanks in advance and sorry for any wrong tags.