下列选项中不属于即时交流的网上交流方式的是（）。
A.QQ
B.MSN
C.飞讯
D.Email
参考答案：D
计算：sin21°+sin22°+sin23°+…+sin288°+sin289°+sin290°=______．
I study really hard ________ I can make my dream come true.
A．to
B．in order to
C．so that
D．because
