题目

Math is one of the most boring classes for many students. But recently, at the University of California in the US, a 1 class got 400 students interested. There were even another 35 2 from behind windows. 3 could make a boring subject so interesting? Terence Tao, the 31-year-old university teacher, is known as “the Mozart of Math”. Tao, born in Hong Kong, spent his childhood in Australia. He showed his great 4 in math when he was very young. At the age of two, he could read. At nine, he went to college math classes. At twenty, he got his doctor’s degree(博士学位). Last summer, T如图，点E在正方形ABCD的边BC上，将△ABE沿直线AE折叠，使点B落在正方形内点P处，延长EP交CD于点F，连接AF．若点E在BC上移动，则下列结论正确的是（ ▲ ）  A．△AEF的周长不变B．△AEF的面积不变C．△CEF的周长不变D．△CEF的面积不变