某砂质边坡砂土的内摩擦角为45°边坡倾角为30°该边坡的稳定系数为()。
A、1.7
B、0.6
C、1
D、1.35
参考答案：A
在（1+x）+（1+x）2+…+（1+x）6的展开式中，x2项的系数是（ ）。（用数字作答）
J. R. Firth’s main approach to the notion of function in context was by means of concept system. People refer to his theory as ______ theory.
