The correct option is A Decrease in infant mortality rate (IMR)
Infant mortality rate (IMR) is the number of deaths per 1,000 live births of children under one year of age. Decrease in IMR will increase the number of newborns and hence the population size will also increase.
Increase in maternal mortality rate (MMR), that is increase in the number of deaths of the mothers at the time of delivery will reduce the size of the population.
Raising the minimum age of marriage for both males and females improves the reproductive health of the society and also helps to achieve the goal of smaller families.
Induced abortion is termination of pregnancy and it reduces the size of the population.