求教一逻辑单题

misty513UID: 3449292

Excluding purchases by businesses, the average  amount spent on a factory-new car has risen 30 percent in the last five years. In the average household  budget, the proportion spent on car purchases has  remained unchanged in that period. Therefore the  average household budget must have increased by  30 percent over the last five years.

Which of the following is an assumption on which  the argument relies？
(A)The average number of factory-new cars purchased per household has remained unchanged  over the last five years.  
(B)The average amount spent per car by businesses  buying factory-new cars has risen 30 percent in  the last five years.   
(C)The proportion of the average household budget  spent on all car-related expenses has remained  unchanged over the last five years.  
(D)The proportion of the average household budget  spent on food and housing has remained  unchanged over the last five years.
(E)The total amount spent nationwide on factory- new cars has increased by 30 percent over the  last five years.