Zero population growth would be more likely to occur in a country in which

I believe the answer is: education levels among women increase.

Studies show that as educations levels among women increase, the awareness of the hardship that they might encountered when they're having too many children (or too early) started to increase. This could lead to small number of newborns and lead to zero population growth.

Fiscal policy because it refers to the use of government spending and tax policies to influence macroeconomic conditions, including aggregate demand, employment, inflation, and economic growth.