TFS阿尔卑斯系列的功效？
参考答案：
适合油性混合性肌肤，补水保湿清爽，收毛孔，抗辐射
----- Can you use chopsticks, John?
----- ________ . I once stayed in China for two years.
A．No problem
B．It all depends
C．I’m sorry, but yes
D．You can forget it
证明：当n为正整数，且nπ≤x(n+1)π，有2n≤S(x)＜2(n+1)．
