Evaluate the indefinite integral ${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}\frac{xdx}{1-x^2}.$

Select one:

a$.-\frac{1}{2}ln(1-x^2)C$

b$.-\frac{1}{2}ln(1x^2)C$

c$.-\frac{1}{2}ln|1-x^2|C$

d$.\frac{1}{2}ln|1-x^2|C$