The Internet is a way of life for US college students. A recent survey by Harris Interactive and 360 youth found that 93 per cent of American college students visit the Internet, and this market is expected to grow from 15.2 million in 2003 to 16.4 million in 2007.That is slow but it could be the result of the already high number of Internet college users. About 88 per cent of American college students own a computer, and more than half have broadband (宽带) connections. Furthermore, 67 per cent own cell phones and 36 per cent use their mobile devices to visit the Internet.Study findings show that 42 per cent go online mainly to communicate socially, and 72 percent of college students check emails at least once a day, with 66 per cent using at least two email addresses. The most popular online social activity is sending messages to friends or family, with 37 percent of college students saying they do so.The study also looked beyond the Internet surfing habits and into the buying habits of this group, and found them responsible for more than $ 210 billion in sales last year alone. College students have learned how to spend their money, with 93 per cent saying low prices are important when shopping.The study also shows that 65 per cent make loan (贷款) payments; 41 per cent of freshmen have a credit card; and 79 per cent of seniors have a credit card. A great number of charges on those credit cards are likely to be for entertainment and leisure expenses. What are the two main points that the survey by Hiarris Interactive look into().

A. Computer and cell phone.
B. College students and their university.
C. Emails and letters.
D. College students’ surfing habits and buying habits on the Internet.