Answer:
d. Involves one step and occurs with inversion of configuration.
Step-by-step explanation:
SN2 reaction mechanism -
It is the type of substitution reaction , where , the reaction takes place in a single step , and in the single step the leaving group get removed and the incoming nucleophile get attached to the reaction center .
This type of reaction is known as SN2 reaction .
In this type of reaction , the reaction is carried out via inversion of configuration , i.e. , the configuration of the reactant and product is exactly opposite to each other .
Hence , from the given options , the correct option for the SN2 reaction mechanism is (d).