Which of the Following Pairs Forms a Fundamental Set of Solutions

Multiple Choice

Which of the following pairs forms a fundamental set of solutions of the Cauchy Euler differential equation .

A) $\{\cos (6 \ln x) , \sin (6 \ln x) \}$
B) $\left\{x^{6} \cos (\ln x) , x^{6} \sin (\ln x) \right\}$
C) $\{\ln (\cos (6 x) ) , \ln (\sin (6 x) ) \}$
D) $\left\{x^{-6}, x^{6}\right\}$
E) $\{\cos (\ln (6 x) ) , \sin (\ln (6 x) ) \}$