Any present or past examples for Monopoly and perfect competition?

Petrol Bunks are best example for perfect competition.The reason is all sellers sell same product with same price .The product differences if any is also same (like ordinary petrol /diesel & extra premium petrol /Diesel)

Stock Market also exhibits perfect competition.

In oligopoly market there are different sellers with product differential being wide in terms of technology & price. E.G, Mosquito repellents ,where cotton nets with repellent coating, coils, electronic repellents, repellent frequency sound wave repellents are seen in markets .Buyers who are rich will buy costly repellents & others will buy low priced items.

Monopoly market represent single seller & many buyers. LIC India enjoyed for many years monopoly in Life Insurance market. Railways in India is monopoly controlled by Central Government Railway Ministry . similarly petroleum product distribution is dealt by Petroleum ministry. Oil &

Natural Gas Commission is having monopoly.

Any producer with break through technology offers a product or service having no competitors enjoys monopoly. For sometime Maruti Udyog Ltd enjoyed monopoly over their spare parts.