The correct statements regarding the demographic trends of places around the world are:
a: The world's population is getting older on average because of long life expectancy in some places. - This statement is true, as many countries, particularly in developed regions, are experiencing an increase in the average age of their populations due to improved healthcare and longevity.
b: The world's population is declining because the population replacement level is not being reached. - This statement can be true in specific contexts. Many developed countries are facing declining populations because their fertility rates are below the replacement level of 2.1 children per woman.
d: The world's population is getting younger on average because of high fertility rates in some places. - This statement is also true, as many developing countries have higher fertility rates, which contributes to a younger global population.
c: More developed countries have longer life expectancy because of high fertility rates. - This statement is not true. More developed countries generally have lower fertility rates but higher life expectancies due to better healthcare, nutrition, and living conditions.
In summary, statements a, b, and d are true regarding the demographic trends of the world, while c is false.