Crenkotown, USA has a large population of Korean Americans. Some of them make a living by delivering otherwise hard to find comforts of home to their fellow countrymen and women. In Crenkotown, between 1957 and 1971, commercial delivers of kimchi- a staple Korean food-increased from 12 to 25. However, during the same time period the number of Koreans living in Crenkotown stayed roughly constant. Therefore, it is unlikely that many more Crenkotownies had kimchi delivered in 1971 than in 1957.
The conclusion rests on which of the following assumptions ?
A. In 1971, most Korean-Americans living in Crenkotown purchased kimchi deliverires from a commercial delivery service
B. In 1971, almost all of those who wanted kimchi delivered were within the range of a delivery service
C. Not all of the kimchi available for delivery in Crenkotown in 1971 were of the same variety pr quality
D. None of the commercial operations that started delivering kimchi after 1957 serviced areas in Crenkotown that didn't formerly have delivery service.
E. Per capita demand for kimchi among Korean-Americans in Crenkotown want unchanged from 1957 to 1971.
I don't get the answer plz help me

the author concludes that the number of people who received the products did not increase.
This of course he says because even though the number of products sold increased, the population of the area didn't.
The assumption made here is that the company serviced ALL the possible areas / people in 1950's itself.
Option D makes sense, thus.