Coal India Option strike price is reduced by Rs.5.25 Why ?

Today Option Strike prices of CoalIndia is reduced by Rs. 5.25. What is the rule behind reducing option strike price of any stock. Please explain/Discuss. Thanks

Hy @pradeep_arora1 this usually happens during Corp actions. In this case dividends.

You can check on this link to know more about the effects of Corporate Actions.