If $n_e$ and $n_h$ are electron and hole concentrations in an extrinsic semiconductor and $n_i$ is electron concentrations in an intrinsic semiconductor, then

• A

  $\left(\frac{n_e}{n_h}\right)=n_i$
• B

  $\left(n_e+n_h\right)=n_i$
• C

  $\left(n_e-n_h\right)=n_i^2$
• Correct answer
  D

  $n_e n_h=n_i^2$

Hence, the correct answer is option: 'D'.