题目

One of the amazing things about the World Wide Web is that anyone can create a    1   page. If people find your page interesting, they will come to   2   it. If lots of people like your page, then you have created something of value. The whole idea of a TV station is to create a place that attracts lots of people. Then the station’s owner can charge companies for   3   on TV.  A web page is like a smart TV station. If yours becomes very popular, then you can   4   ads on it.  That is one form of “value”. There are other forms as well, especially for teenagers. 5．某双链DNA分子含有1000个碱基对，已知腺嘌呤（A）数目是300个，则胞嘧啶（C）的数目是（　　）A．300B．400C．600D．700