During Diwali celebrations in 2018, which special event entered the Guinness Book of World Records for lighting an extraordinary number of oil lamps along the riverfront to mark the festival of lights?

Introduction / Context:
Diwali, the festival of lights, is celebrated across India with lamps, fireworks and cultural events. In recent years, several state governments have organised large scale public celebrations that seek recognition from record keeping bodies such as the Guinness Book of World Records. One such high profile event was organised in Ayodhya and became famous for lighting an enormous number of earthen lamps along the riverfront, gaining world record recognition and extensive media coverage.

Given Data / Assumptions:

• The question refers specifically to Diwali celebrations in the year 2018.
• It asks which named event entered the Guinness Book of World Records for lighting an extraordinary number of oil lamps.
• The options list Ayodhya Deepotsav and several similarly named events such as Har Har Gange Deepotsav and Varanasi Deepotsav.
• We assume the record concerns a state sponsored event associated with the Uttar Pradesh government.

Concept / Approach:
The approach is to connect current affairs with geography and culture. The government of Uttar Pradesh organised a large scale celebration in Ayodhya called Ayodhya Deepotsav, featuring lakhs of diyas on the banks of the Sarayu river and in surrounding areas. In 2018 this event received Guinness recognition for lighting a record number of oil lamps simultaneously. Recognising the name of the event that achieved this record allows us to select the correct option.

Step-by-Step Solution:
1. Note the key clues: Diwali celebrations, the year 2018, and entry into the Guinness Book of World Records for oil lamps. 2. Recall that the government of Uttar Pradesh began hosting an annual celebration in Ayodhya known as Ayodhya Deepotsav. 3. In 2018, this event lit several lakhs of diyas along the riverfront and in the city, and Guinness adjudicators certified a world record in terms of the number of lamps lit simultaneously. 4. Among the options, Ayodhya Deepotsav is the only event that is both named this way and specifically associated with the 2018 Guinness record for Diwali lamps. 5. Therefore, select Ayodhya Deepotsav as the correct answer.

Verification / Alternative check:
News reports from 2018 confirm that Ayodhya Deepotsav, organised by the Uttar Pradesh government, received a Guinness World Record certificate for lighting an unprecedented number of earthen lamps. Images and official statements mention Ayodhya and the Sarayu river specifically. Other riverfront celebrations, such as events in Varanasi, also feature diyas and cultural programmes but did not receive the same Guinness recognition in 2018 for a lamp lighting record of this scale, which reinforces the conclusion that Ayodhya Deepotsav is the correct event.

Why Other Options Are Wrong:

• Har Har Gange Deepotsav sounds like a celebration connected with the Ganga river but does not refer to the specific Ayodhya event that obtained the Guinness record in 2018.
• Varanasi Deepotsav would logically refer to a festival in Varanasi, a different city on the Ganga, and is not the one recognised by Guinness in 2018 for this particular lamp record.
• Ganga Deepotsav is a generic sounding name and is not the official title of the Ayodhya event that entered the Guinness Book of World Records in that year.

Common Pitfalls:
A frequent mistake is to confuse Ayodhya with Varanasi because both cities are in Uttar Pradesh and associated with major Hindu religious traditions and riverfront Aarti ceremonies. Another pitfall is to focus only on the word Ganga and assume that the record must relate to an event explicitly named after the river. Candidates may also overlook the specific year 2018 and mix it up with later record attempts. Careful attention to the name Ayodhya Deepotsav and its widely publicised Guinness recognition helps avoid these errors.

Final Answer:
The Diwali event that entered the Guinness Book of World Records in 2018 for lighting a record number of oil lamps was Ayodhya Deepotsav.