“Famines were also a major and recurring source of increased mortality.” Which of the following is not a cause of famines?

These are the options for the question :“Famines were also a major and recurring source of increased mortality.” Which of the following is not a cause of famines?

a) Continuing poverty and malnutrition in an agro-climatic environment.
b) Inadequate means of transport and communication.
c) Failure of entitlements
d) Increasing birth rates

The correct answer is -d.