A. ±3

B. 3

C. ±9

D. 9

The coefficient of x^{n} in(1+x)^{2}/(1-x)^{2} is

The term independent of x in (x+1/x)^{6} is

The sum of the coefficients of even powers of x in the expansion of (1+x+x^{2})^{15} is