What is the path difference of destructive interference 

• A

   $\mathrm{n\lambda }$

• B

  $\mathrm{n}(\mathrm{\lambda }+1)$

• C

  $\frac{(n+1)\lambda }{2}$

• D

  $\frac{(2\mathrm{n}+1)\mathrm{\lambda }}{2}$