[求助]GMAT的逻辑中假设类的题该怎么做啊?

On turning 65 years old, everyone living in the town of Malton becomes eligible to receive a card that guarantees discounts on most goods and services sold in the town. Census records for 1990 show that 2450 inhabitants of Malton turned 64 in that year. Yet, in 1991 over 3000 people applied for and properly recerved discount cards. So clearly some of Malton's population growth between 1990 and 1992 must be attributable to migration into the city by people in their mid-60's.

Which of the following is an assumption on which the argument depends?

A. The town of Malton has no complete census records for 1991.

B. The overall size of the population of Malton grew by over 500 during 1990.

C. Fewer people applied for and received discount cards in 1991 and did so in 1992.

D. Among the people 65 years old or older who moved into Malton in 1991, there was no one who did not apply for a discount card.

E. In general, people who applied for and received discount cards in 1991 first became eligible to do so in that year.

请各位大牛写出解题的思维过程,我在后面公布答案,谢谢大家帮忙^_^