Question

Which of the following are the reasons for the smog being visible in the month of November December in Delhi

Answer 1

The increasing levels of pollution made it impossible to live in Delhi
As it is winter season and since smoke gets mixed with fog it creates smog

Answer 2

smog is made up of smoke and fog and in the month of november and december this is winter season in India means fog can be seen in these months and also Delhi is very polluted city where smokes from the cars and bikes are common so when they are combined they produce smog. 
May this answer will help you so please please mark it as a brainliest answer