The correct answer is B. scarcity.
Dearth means a lack of something, especially something that is needed or wanted. In this case, there is a lack of milk in Delhi. This could be due to a number of factors, such as a shortage of cows, a lack of rainfall, or an increase in demand.
Extravagance means spending more money than is necessary or reasonable. In this case, there is no indication that people in Delhi are spending more money on milk than they need to.
Abundance means a large quantity or number of something. In this case, there is not a large quantity of milk in Delhi.
Sufficiency means the amount or quantity that is necessary or adequate. In this case, there is not a sufficient amount of milk in Delhi.