University of Oxford is the oldest university in the English-speaking world and it's one of the top universities in the world. There is no clear date when the university started, but teaching began at Oxford in some forms in 1096 and developed quickly from 1167.
    There are 39 independent（独立的）colleges at Oxford, attracting students and learned men from across the world. There are over 100 libraries for the students and learned men to use. At University of Oxford, they also provide a number of money for the best students. Of course, if you want to study here, first you have to reach a certain level of English language.
    College life at Oxford is very exciting but busy. The groups of college provide a friendly and welcoming home for students while the colleges are strict with students about their studies. Many Chinese students are studying here. The number of Chinese students at the university has grown quickly over the past 10 years.
根据短文内容，选择最佳答案。

关于函数f（x）=cosxsin2x，下列说法中正确的是____

①y=f（x）的图象关于（π，0）中心对称；②y=f（x）的图象关于直线x= $\frac{\pi }{2}$ 对称

③y=f（x）的最大值是 $\frac{\sqrt{3}}{2}$ ；         ④f（x）即是奇函数，又是周期函数．