The news from America’s housing market is getting no better. As sales declines and defaults and foreclosures climb, pessimists fear that over a million Americans could be driven out of their homes as adjustable-rate mortgages are reset. What should policymakers do Congress is eager to do more: hence the calls to expand the role of Fannie Mae and Freddie Mac, the giant government-sponsored enterprises (GSES) that tower over America’s mortgage market.

Fannie’s and Freddie’s political allies want two things. The first is the raising of the $417,000 limit on the size of loans that the pair may handle. The second demand is the lifting of caps on the amount of mortgages they may buy and hold for themselves. Fannie and Freddie could then ride to the rescue of struggling borrowers, injecting liquidity into parts of the market that have seized up. Their arguments are winning support, and opposition from the Bush administration and the GSES’ regulator is softening. Unfortunately, the ideas are likely to do more for Fannie and Freddie than for the mortgage market.

Start with the $417,000 limit. Lifting this could help if Fannie and Freddie scoured the upper bracket for borrowers who were struggling but viable. But their history suggests that they would cherry-pick those who could get refinanced elsewhere. And the huge-mortgage market may be correcting itself anyway: spreads over GSE-backed loans, though still unusually high, are falling.

It is also riskier. When they hold a mortgage, they take on not only credit risk but also interest-rate and prepayment risk. The loans they guarantee, in contrast, carry only credit risk. So as well as being just as effective, the guarantee business is also safer—and thus better for the taxpayer who unwittingly stands behind the GSES.

Moreover, even if they grow no more, the mortgage giants pose a clear systemic threat. Their portfolios of retained mortgages and mortgage-backed securities add up to no less than $1.4 trillion. It is bad enough that this is concentrated in two institutions. No matter how much risk they take or how they manage it, they can borrow at rock-bottom interest rates. If they got into trouble, banks as well as taxpayers would be on the hook. Banks may hold as much GSE debt as they want. Many have amounts that exceed their regulatory capital.

The giants were set up decades ago to help banks pool concentrated regional mortgage risk and to make housing more affordable. But as the market has grown deeper and more sophisticated, history has left them behind—hence their desire to get into any bit of the business that will turn a profit. The eventual aim should be to turn them into normal private-sector companies, by stripping them of the charters that give rise to the implicit government guarantees, and break them into smaller pieces.

What can be inferred about the Fannie and Freddie from Paragraph 2 and 3（）

A. They are companies of normal size for mortgage and loan

B. They are companies supported by the government

C. They are companies functioning as banks

D.They are companies that have no help to the housing market