单选题：Questions are based on the following passage.When we talk a

Questions are based on the following passage.
When we talk about Americans barely into adulthood who are saddled with unbearable levels of debt, the conversation is almost always about student loan debt．But there's a growing body of evidence suggesting that today's young adults are als0 drowning in credit-card debt--and that many of them will take this debt to their graves.
More than 20% overspent their income by more than $100 every single month．Since they .haven't built up their credit histories yet, it's a safe bet that these young adults are paying relatively high interest rates on the resulting credit card debt.
Although many young people blame "socializing" as a barrier to saving money, most of them aren't knocking back $20 drinks in trendy (时尚的)lounges．They're struggling with much more daily financial demands.
To a disturbingly large extent, the young and the broke are relying on credit cards to make it until their next payday．This obviously isn't sustainable in the long run, and it's going to put a huge drag on their spending power even after they reach their peak earning years, because they'll still be paying interest on that bottle of orange juice or box of spaghetti (意式面条)they bought a decade earlier.
A new study out of Ohio State University found that young adults are accumulating credit card debt at a more rapid rate than other age groups, and that they're slower at paying it off． "If what we found continues to hold true, we may have more elderly people with substantial financial problems in the future," warns Lucia Dunn, professor of economics at Ohio State． "If our findings persist, we may be faced with a financial crisis among elderly people who can't pay off their credit cards."
Dunn says a lot of these young people are never going to get out from under their credit card debt."Many people are borrowing on credit cards so heavily that payoff rates at these levels are not sufficient to recover their credit card debt by the end of their life, which could have loss implications for the credit card issuing banks."
What is the main idea of the first paragraph? A．Many young Americans will never be able to pay off their debts.
B．Credit cards play .an increasingly important role in college life.
C．Credit cards are doing more haxm than student loans.
D．The American credit card system is under criticism.