Assertion`:` `[Co(NO_(2))_(3) (NH_(3))_(3)]` does not show optical isomerism.
Reason`:` It has a plane of symmetry.
A. If both assertion and reason are true and the reason is the correct explanation of the asserion .
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. if assertion is true but reason is false.
D. If the assertion is false but reason is true