Use a change of variables to evaluate the following definite integral. -2 x√4-x² dx Determine a change of variables from x to u. Choose the correct answer below. OA. u= A. u = √4 u = √4-x² B. u = x² O c. u=4-x² ○ D. u = 2x1 Write the integral in terms of u. { x√4-x² dx = √ -2 0 Evaluate the integral. SX -2 x√4-x² dx= (Type an exact answer.) du