The energy levels of a certain atom are $A, B,$ and $C$ in increasing order of energy,i.e.,$E_A < E_B < E_C$. If $\lambda_1, \lambda_2,$ and $\lambda_3$ are the wavelengths of radiation corresponding to transitions from $C$ to $B$,$B$ to $A$,and $C$ to $A$ respectively,which of the following relations is correct?

• A
  $\lambda_1, \lambda_2, \lambda_3 = 0$
• B
  $\lambda_3 = \lambda_1 + \lambda_2$
• C
  $\lambda_3 = \frac{\lambda_1 \lambda_2}{\lambda_1 + \lambda_2}$
• D
  $\lambda_3^2 = \lambda_1^2 + \lambda_2^2$