单选题：Questions are based on the following paassage.Virtually un

Questions are based on the following paassage.
Virtually unknown a decade ago, big online teacher education program snow dwarf their traditional competitors, outstripping (超过) even the largeststate university teachers' colleges.
A USA Today analysis of newly released U. S. Department of Education data finds that four big universities, operating mostly online, have quickly become the largest education schools in the USA. Last year the four--three of which are for-profit--awarded one in 16 bachelor' sdegrees and post-graduate awards and nearly one in 11 advanced education awards, including master' sdegrees and doctorates.
A decade ago, in 2001, the for-profit University of Phoenix awarded 72 education degrees to teachers, administrators and other school personnel through its online program, according to federal data. Last year, it awarded nearly 6,000 degrees, more than any other university.
Traditional colleges still produce most of the bachelor's degrees in teaching. But online schools such as Phoenix and Walden University awarded thousands more master's degrees than even the top traditional schools, all of which are pushing to offer online coursework.
"We shouldn't be surprised because the whole industry is moving in that direction," said Robert Pianta, dean of the University of Virginia's Curry School of Education. "The thing I would be interested in knowing is the degree to which they are simply pushing these things out in order to generate dollars or whether there's some real innovation in there. "
For-profit universities have been the subject of intense examining in Congress. Tom Harkin, D-Iowa, who chairs the Senate Health, Education, Labor and Pensions Committee, last week released findings from a two-year investigation showing that they cost more than comparable not-for-profit schools and have higher dropout rates. For-profits, the investigation found, enroll about 10% of U. S. college students butaccount for nearly 50% of student loan defaults.
Online education schools, many of which have open-enrollment policies similar to community colleges, say their offerings are high quality.
Meredith Curley, dean of the University of Phoenix College of Education, said many students are returning to complete their education after starting families and changing careers. Their average age is 33, she said, and many work while they attend classes. Becky Lodewyck, Phoenix's associate dean, said teaching candidates must complete at least 100 hours of field experience. She said online classes are "incredibly dynamic" and have the potential to hold students more accountable than face-to-face classes.
"You can't hide," she said. "Everyone participates--everyone has to be fully engaged in the work. "
It can be learned from the second paragraph that four big universities______. A．have become the largest online schools in the US
B．are the biggest for-profit schools in the US
C．occupy important position in education in the US
D．focus on developing advanced education in the US