(c) R−S− configuration is related to the enantiomers, which are optically active. (:.true) (b) The mixing of two optically-active compounds (d and l -type ) in equimolar quantity is called racemisation (: true) (c) A molecule containing plane of symmetry does not show optical-activity. Hence, the given statement is false. (d) Optical isomers that are not enantiomers are called diastercoisomers (is true). (e) All chiral objects are asymmetric (true). ∴(c) is the correct answer.