题目

Almost every college and university in the US now offers some forms of Internet–based application. However, students may miss a lot when they only use Internet information to make their college decisions. Some people believe that the best way to get a detailed look at what life is like at any college or university is by visiting the campus.At present, school visits are becoming popular in the US. Most students begin visiting colleges and universities that they are interested in before their final year of high school. The majority of colleges and universities let interested students visit the已知函数f(x)=px-p-lnx(p＞0)是增函数．（I）求实数p的取值范围；（II）设数列{an}的通项公式为an=2n+1n，前n项和为S，求证：Sn≥2ln（n+1）．