脊髓灰质炎减毒活疫苗初种次数为（）。
A.1次
B.2次
C.3次
D.4次
E.5次
参考答案：C
设直线kx+（k+1）y-1=0与坐标轴所构成的直角三角形的面积为Sk，则S1+S2+…+S2008=______．
The sun's appearing to rise in the east is () the revolution of the earth on its axis from west to east.
A．owe to
B．due to
C．as to
D．as for
