目前，A股主承销商的净资本最低为（）。

A.人民币2000万元

B.人民币2亿元

C.人民币5000万元

D.人民币5亿元

This is offered as a textbook illustration of the principle that voters are far shrewder than most politicians believe. This case study highlighting Washington’’s inability to fool anyone is based on a recent survey of the attitudes of people on Medicare about their new prescription-drug benefit.Last fall, when Congress added prescription-drug coverage to Medicare, the new law was hailed as a political masterpiece. Congressional Democrats, who overwhelmingly opposed the bill, thundered that they, too, were eager to provide a drug benefit under Medicare, but they championed alternative legislation that offered a larger drug subsidy and smaller incentives to health insurers to participate. Liberals such as Sen. Edward Kennedy were confident that the drug bill, with plenty of holes in its benefit formulas, would inevitably be expanded around the time it took effect.Not many in Congress seemed troubled that the federal budget was deep in deficit, the nation was saddled with future expenditures for the Iraq war and virtually no health care expert believed that the legislation would fit into its projected $400-billion-over-10-years cost framework. The new law was a cynical bargain that had more to do with the 2004 election than a rational approach to the prescription-drug needs of the nation’’s elderly.The prescription-drug legislation seems a compromise between competing ideologies inserted into a fixed congressional budget. Put another way, it was sausage-stuffing in the guise of lawmaking. And, what no one anticipated was the reaction of the elderly, a group that votes in disproportionate numbers.

Also found in Paragraph 1, what does "this case study" probably refer to

A．A case study the writer is to talk about.

B．Part of a textbook on politics.

C．What the author is going to write.

D．Washington’s inability to fool anyone.